Peer Revenue Now accepting positions

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Condensed Matter Materials Science

cond-mat.mtrl-sci Watch Materials Science

Wednesday 15 July

Materials Science

Temperature-driven sodium-ion dynamical-to-static crossover in the zig-zag ordered phase of Na$_{0.5}$CoO$_2$

Shangfei Wu, Hengxin Tan, Dong Wu et al. (+7 more)

We employ polarization-resolved Raman spectroscopy combined with first-principles calculations to study the sodium-ion lattice dynamics in a sodium zig-zag ordered cobaltate compound Na$_{0.5}$CoO$_2$. We detect two sodium phonon modes for the first time, and their mode frequencies are consistent with first-principles phonon calculations based on an orthorhombic unit cell. We find that they appear below around $T^*\sim300\pm50$K with large linewidth broadening, much lower than the sodium zig-zag ordering temperature $T_\text{S}\sim460$K, and then narrow at lower temperatures. We interpret the sodium-phonon anomalies occurring at $T^*$ as a dynamical-to-static crossover involving mainly the motion of sodium ions. Our results suggest that the gradual freezing of the sodium ions and the well-defined static sodium-zigzag order below $T^*$ set the stage for the emergent electronic and magnetic orders in the CoO$_2$ layer of Na$_{0.5}$CoO$_2$.
Read the full abstract

All authors Shangfei Wu, Hengxin Tan, Dong Wu, Mingshu Tan, Xinyu Zhou, Tianchen Hu, Tao Dong, Feng Jin, Qingming Zhang, Nanlin Wang

Materials Science

First-principles Study of Structural and Electronic Properties of Mn-doped Cu2NiXY4 (X=Sn, Ge, Si; Y=S, Se) Chalcogenide Semiconductors

Iskandar Raufzoda, Dilshod Nematov and Amondullo Burhonzoda

In this work, the effect of partial substitution of Mn by Ni on the structural and electronic properties of kesterite systems Cu2NiXY4 (X = Sn, Ge, Si; Y = S, Se) was studied using density functional theory (DFT). The mBJ+U method was used to characterize the bandgap more accurately. To the best of our knowledge, a systematic comparative study of Mn substitution in the entire Cu2NiXY4 (X = Sn, Ge, Si; Y = S, Se) family has not been previously performed. Due to crystallographic constraints of the kesterite unit cell, the substitution of a single Ni atom with Mn corresponds to 50%. This configuration was chosen to study the effect of Mn substitution on the structural and electronic properties of Cu2NiXY4 (X = Sn, Ge, Si; Y = S, Se) compounds, whereas the study of lower concentrations requires the use of a supercell and is the subject of further research. The calculation results show that the partial substitution of Ni with Mn preserves the tetragonal structure of kesterite and significantly alters the electronic structure. In all the compounds studied, the bandgap decreases from 1.028-3.397 to 1.007-3.333 eV. For example, in the Cu2NiSnS4 system, the bandgap width decreases from 1.59 eV to 1.49 eV. The narrowing of the bandgap results from hybridization between the Mn-3d, Cu-3d, and S/Se-p orbitals near the band edges, leading to a redistribution of electronic states around the Fermi level. The results demonstrate that Mn substitution is an effective strategy for controlling the electronic properties of Cu2NiXY4 kesterites, offering great promise for use in optoelectronic devices where adjustable bandgaps are required.
Read the full abstract

Materials Science · Cross-listed from physics.comp-ph

A Showcase of Using the Partial-Structure R1 to Assemble Small-Molecule Crystal Structures

Xiaodong Zhang

Using a few concrete examples this paper has demonstrated a few observations on using the partial-structure R1 (pR1) to assemble small-molecule crystal structures. (1) Assembling can start with orienting and/or placing large fragments or small fragments containing heavy atom(s). (2) It is handy to attach a fragment to a partial model as only the orientation needs to be optimized. (3) In a structure containing heavy atoms it is impossible to directly calculate the orientations of a light-atom-only fragment. Instead, it is necessary to use residual reflection intensities in which the contribution of the partial model containing all heavy atoms is deducted away. These observations indicate that pR1 is a useful tool for solving some small-molecule crystal structures.
Read the full abstract

Materials Science

Mapping recrystallization trajectories in GaAs using latent space diffraction analysis

Ellis Rae Kennedy, Kwanghwi Je and Erik Thiede

Recrystallization in disordered solids proceeds through a sequence of local structural rearrangements that are difficult to resolve using conventional diffraction analysis. In amorphous and partially ordered materials, subtle variations in diffuse scattering, short-range order, and defect-mediated symmetry emergence encode the pathways through which ordering initiates and propagates. Here, we introduce a latent space framework for mapping these pathways directly from in situ 4D-STEM diffraction data. A convolutional autoencoder provides a compact representation of structural motifs, and unsupervised clustering identifies recurring microstructural states, including amorphous, paracrystalline, crystalline, twinned, and hybrid intermediates. By tracking these states across temperature, we construct phase trajectory models that reveal the topology of the recrystallization landscape, including metastable basins, branching pathways, hybrid states, and temperature-dependent reorganizations of accessible states. Applied to ion irradiated GaAs, this approach uncovers two distinct recrystallization regimes separated by a transition near 250\textdegree{}C. At low temperature, recrystallization is growth-dominated and dominated by the persistence of amorphous and crystalline states. At high temperature, the transformation landscape reorganizes: hybrid and faulted states become metastable precursors to twinning, polycrystalline regions stabilize, and twinned structures emerge as dominant end states. The latent space representation also identifies amorphous patterns with weak symmetry signatures that precede recrystallization. This reveals structural precursors to ordering that are not captured by conventional descriptors give new insights into how recrystallization is initiated.
Read the full abstract

Materials Science · Cross-listed from cond-mat.soft

Microscopic constitutive theory of stress overshoot, yielding, and strain hardening in amorphous materials

Ankit Singh, Valeriy V. Ginzburg and Alessio Zaccone

We develop a microscopic constitutive theory for the nonlinear deformation of metallic and polymer glasses based on nonaffine elasticity coupled to irreversible many-body relaxation. The theory predicts the full stress–strain response, from linear elasticity through stress overshoot and yielding to steady plastic flow. We show that stress overshoot originates from the competition between a nonaffine elastic instability induced by strain-driven loss of mechanical connectivity at the atomic/molecular level, and viscous dissipation associated with structural relaxation. For polymer glasses, finite chain extensibility naturally accounts for strain hardening at large deformation. The stretched-exponential relaxation exponent is obtained independently from stress or modulus relaxation measurements and provides the primary dynamical input to the theory. Using a small set of physically meaningful parameters, the model quantitatively reproduces experimental stress–strain curves for metallic glasses, polycarbonate, PMMA, and epoxy resins over a broad range of strain rates. These results establish a unified microscopic framework linking relaxation dynamics, yielding, plastic flow, and strain hardening in amorphous solids.
Read the full abstract

Materials Science · Cross-listed from cs.LG

Microstructure-Conditioned Surrogate Models for Graded Multiscale Optimization of Mycelium Composites

J. Storm, I.B.C.M. Rocha, S. Schyck et al. (+2 more)

Emerging sustainable materials increasingly rely on engineered hierarchy and microstructure to achieve control of their properties and mechanical behavior. Optimizing these materials with controllable microstructures requires efficient multiscale simulations. Data-driven surrogate models for the microscale can accelerate multiscale simulations, but require large amounts of data even for a fixed microstructure. When a range of microstructures is considered, as is the case in multiscale optimization, even more data is needed to train a surrogate. To overcome this challenge, we condition a hybrid physics-data surrogate on microstructural variables using a hypernetwork. This approach enables accurate predictions of multiscale mechanical behavior for a mycelium-woodchip composite material, even when trained on small datasets. The conditioned surrogate makes multiscale simulations of functionally graded structures tractable, and we validate it against a full FE^2 simulation. We optimize a graded multiscale disk, and reduce the peak stress by 43% compared to one with a random microstructure. Then, we go one step further, conditioning the network directly on manufacturing variables that can have a complex influence on the microstructure. This is a practical route to engineer the microscale for desired macroscale behavior. This contribution highlights the benefits of microarchitectured structures and demonstrates how conditioned surrogate models enable their multiscale optimization, which will accelerate the development and design of future sustainable materials and structures.
Read the full abstract

All authors J. Storm, I.B.C.M. Rocha, S. Schyck, K. Masania, F.P. van der Meer

Materials Science

Role of small-radius and high-electronegativity A-Site dopants in enhancing proton transport and stability of perovskite electrolytes

Hang Ma, Ying Liang and Tianxing Ma

The practical application of BaCeO$_3$-based electrolytes is limited by their poor chemical stability in proton-conducting solid oxide fuel cells. Commonly employed B-site doping strategies typically improve proton transport with limited improvement in stability. Recent experiments show that A-site Ca doping can simultaneously enhance both properties. Here, through first-principles calculations and mechanistic analysis of Ca-doped BaCeO$_3$, we identify the synergistic roles of small-radius, high-electronegativity A-site dopants in governing proton transport and chemical stability in perovskite electrolytes. We show that the higher electronegativity of A-site dopant weakens the A-O ionic bonding, facilitating oxygen-vacancy formation and enhancing proton uptake by increasing the basicity. This weakened A-O interaction also suppresses the formation of impurity phases and reduces the adsorption strength of acidic gases such as CO$_2$ and SO$_2$. The lattice contraction induced by the smaller ionic radius improves thermal stability and can enhance proton diffusion in systems where proton transfer is the rate-limiting step. Furthermore, we find that Ca surface segregation can mitigate grain-boundary resistance effects. Our results demonstrate the advantages of A-site Ca doping in Ba-based electrolytes, clarify the mechanisms by which small-radius, high-electronegativity dopants influence proton transport and chemical stability, and provide guidance for the design of high-performance proton-conducting electrolytes.
Read the full abstract

Materials Science

Research progress in high-pressure tuning of layered magnetic materials

Yue Dongdong, Gao Xin, Mu Congpu et al. (+2 more)

Two-dimensional van der Waals materials have enormous potential applications in many fields due to their unique layered structure and excellent properties. Compared with three-dimensional bulk materials, layered systems are coupled by weak van der Waals interactions between layers, endowing them with much higher structural compressibility, particularly along the interlayer direction, which is more sensitive to external pressure. High pressure can expand the accessible phase space, enabling the synthesis of new materials or the retention of metastable phases. On the microscopic level, pressure can significantly tune the interlayer structure and interactions, induce changes in the electronic structure, and consequently give rise to a variety of rich physical properties. This article systematically introduces in situ high-pressure experimental approaches, including diamond anvil cells combined with X-ray and spectroscopic techniques, high-pressure magnetic transport measurements, and emerging NV-center quantum sensing. It further reviews representative pressure-induced phenomena and underlying tuning mechanisms in layered magnetic materials, such as high-spin to low-spin transitions of transition-metal ions and the accompanying structural phase transitions and superconductivity; substantial enhancement of the Curie temperature and continuous switching of magnetocrystalline anisotropy; and antiferromagnetic-to-ferromagnetic transitions achieved by modulating exchange interactions or via stacking engineering. Finally, we discuss future directions, including synergistic multi-field control by combining pressure with electric fields and twisted heterostructures, as well as strategies such as pressure quenching to retain high-pressure metastable magnetic phases at ambient conditions.
Read the full abstract

All authors Yue Dongdong, Gao Xin, Mu Congpu, Liu Zhongyuan, Zhai Kun

Materials Science

Rotation topological states: theory and material realization

Chun-Xue Liu, Yilin Han, Runze Li et al. (+2 more)

The conventional characterization of topological materials relies on topological invariants calculated from the entire set of occupied bands. However, when a system possesses rotational symmetry, the occupied Hilbert space can be decomposed into multiple subspaces labeled by distinct rotation eigenvalues. We show that this decomposition reveals hidden topological states characterized by a novel $\mathbb{Z}_2^n$ topological invariant, where $n$ is the number of subspaces, while the conventional $\mathbb{Z}_2$ invariant may fail to detect the topology hidden in the rotation subspaces. Remarkably, time-reversal symmetry pairs conjugate rotation eigenvalues and guarantees that the two subspaces have the same $\mathbb{Z}_2$ invariants, making the topology always hidden from the conventional global invariant. We formulate the theory of rotation-subspace topology and demonstrate its material realization in bulk CsCl. Using first-principles calculations and symmetry analysis, we show that bulk CsCl, which is diagnosed as topologically trivial by the conventional approach, features a nontrivial $\mathbb{Z}_2^3$ invariant along the $\Gamma$-R path and a nontrivial $\mathbb{Z}_2^4$ invariant along the $\Gamma$-Z and M-R paths, leading to double Weyl points on the (111) and (001) surfaces, respectively. The subspace $\mathbb{Z}_2^n$ invariant proposed here serves as a necessary refinement for symmetry-protected topological phases and will facilitate the identification of a large class of topological states overlooked by existing diagnostics.
Read the full abstract

All authors Chun-Xue Liu, Yilin Han, Runze Li, Yulong Liu, Zhi-Ming Yu

Materials Science · Cross-listed from cond-mat.mes-hall

Emergent induction in magnetic Weyl semimetals

Takahiro Anan and Takahiro Morimoto

We theoretically study emergent electromagnetic responses in Weyl semimetals. Focusing on magnetic Weyl semimetals, we develop a general theory of emergent induction driven by magnetic dynamics. We show that magnetoelectric (ME) responses in Weyl semimetals give rise to emergent induction mediated by magnetization dynamics. Using effective two-band models for magnetic Weyl semimetals, we derive a formula for the ME response that includes both intraband and interband contributions. The resulting formula shows that the intraband contribution is proportional to the relaxation time $\tau$, whereas the interband contribution is associated with the separation of the Weyl nodes. Applying the general formula to a model of polar Weyl ferromagnets, we demonstrate that the dynamics of the toroidal moment is closely related to the emergent inductive response in polar Weyl ferromagnets, as recently discovered by Suzuki et al. [Y. Suzuki et al. arXiv:2607.12322]. The chemical-potential dependence of the inductance indicates that the emergent electromagnetic response is enhanced in the energy range of the Weyl dispersion, reflecting the topological nature of Weyl semimetals.
Read the full abstract

Materials Science · Cross-listed from physics.optics

Imprinting topology on thermal light

Tianle Chen, Kelsey Everts, Andrew Forbes et al. (+1 more)

Topological structuring of light inevitably leverages on optical coherence to ensure that the imparted spatial phases are preserved, requiring highly coherent sources or coherence engineering embedded in the design. Now we show that thermal light can be spatially engineered to carry optical topologies in the form of Skyrmions. Such topologies are immune to time averaged decoherence, a fact we leverage on in reverse to create metasurface mediated incoherent topologies from a thermal source. The pristine nature of our measured Skyrmions validates the approach, while simulations reveal how coherence management in the metasurface design would further enhance the functionality. Remarkably, the generation stage inherits robustness from the topology, remaining immune to material and fabrication defects. Our work reports the first topologies from purely thermal light, opening a path to exploiting topology in ubiquitous everyday light sources.
Read the full abstract

All authors Tianle Chen, Kelsey Everts, Andrew Forbes, Yungui Ma

Materials Science

Hybridization-controlled re-entrant electronic phase switching and moire-confined states in twisted bilayer PtTe2

Seoung-Hun Kang, Jeonghwan Ahn and Young-Kyun Kwon

Twisting a van der Waals bilayer changes not only the moiré periodicity but also the local stacking and interlayer hybridization. Here, we show, using fully relaxed first-principles calculations including spin–orbit coupling, band unfolding, and Brillouin-zone-integrated densities of states, that bilayer PtTe$_2$ exhibits a non-monotonic evolution between gapless and gapped electronic regimes. The $7.34^\circ$ structure remains gapless, whereas finite direct gaps appear at the sampled intermediate angles. The gap closes at the sampled $60^\circ$ configuration and reopens at higher angles. The direct gap shows an overall increase with the minimum local interlayer Pt–Pt separation, although the complete distribution of local stacking environments is required to account for deviations from this trend. At $7.34^\circ$, the low-energy states are concentrated predominantly in the AA-like regions of the otherwise gapless moiré cell. Controlled interlayer-separation scans show that increasing the layer spacing removes the near-$E_F$ crossings and opens a gap, consistent with weakened interlayer Te-$p_z$ hybridization. These results identify the redistribution of interlayer hybridization as the microscopic origin of the re-entrant gap evolution in twisted bilayer PtTe$_2$.
Read the full abstract

Materials Science

Physics-Informed Residual Deep Learning for Constitutive Modeling of Hot Deformation and Dynamic Recrystallization in a Mo-Rich $\alpha+\beta$ Titanium Alloy

Prashil S. Joshi, Diksha Mahadule and Rajesh K.Khatirkar

Accurate constitutive modeling of hot deformation behavior is essential for designing thermomechanical processes in advanced structural alloys. Conventional Arrhenius-type and empirical models do not adequately capture the combined effects of strain hardening, dynamic recovery (DRV), and dynamic recrystallization (DRX) across broad processing conditions. In this study, two Stacked Residual Physics-Informed Neural Networks (STAR-PINNs) were developed to simulate the hot deformation response of a Mo-rich $\alpha+\beta$ titanium alloy (Ti-6Al-4Mo-1V-0.1Si). The Enhanced STAR-PINN incorporated thermomechanical constitutive constraints, while the DRX-Aware STAR-PINN employed a dual-output architecture to account for recrystallization kinetics. Both models used a shared residual encoder trained on experimental flow stress data collected at temperatures from 800 to 1050 degrees C and strain rates between 0.01 and 10 per second. Physics-informed constraints, including thermal softening, strain-rate sensitivity, strain hardening, and post-peak softening, were enforced through automatic differentiation. The DRX-Aware model further integrated JMAK-Avrami regularization, DRX saturation constraints, and Arrhenius-based consistency with tunable parameters, directly linking the predicted DRX fraction to stress output via latent-feature fusion. The DRX-Aware STAR-PINN achieved RMSE = 11.62 MPa, MAE = 4.73 MPa, R^2 = 0.9852, and a cross-validated RMSE of 12.74 +/- 0.38 MPa. The learned JMAK parameters converged to k = 2.03 and n = 1.99, remaining close to the conventional values while being inferred directly from the data. The model effectively mirrored flow curves influenced by temperature, DRX development, and Zener Hollomon correlations under interpolation scenarios while preserving physically coherent constitutive behavior.
Read the full abstract

Materials Science

Resistivity in Dilute Cu-3d Alloys Governed by Disorder-Induced Band Broadening

Kenji Yamaguchi

The mechanism governing the resistivity in dilute Cu-3d transition-metal alloys at ambient temperature – the regime relevant to most practical applications and distinct from the low-temperature, Kondo-screened regime addressed by earlier theoretical work – is investigated using first-principles calculations based on the Korringa–Kohn–Rostoker coherent potential approximation combined with the Kubo–Greenwood formalism. The paramagnetic state is described within the disordered local moment (DLM) framework, corresponding to a local-moment paramagnet rather than a Pauli paramagnet. We show that the experimentally observed resistivity trends are reproduced only within the DLM description, while nonmagnetic and ferromagnetic states fail to capture the correct element dependence. Contrary to conventional interpretations based on the density of states at the Fermi level, the resistivity exhibits a strong correlation with the full width at half maximum (FWHM) of the Bloch spectral function (BSF) on the Fermi surface. This correlation reflects the disorder-induced lifetime broadening of electronic states, directly related to the scattering rate that governs electrical resistivity. A common power-law scaling between resistivity and BSF broadening is identified across different magnetic states. These results demonstrate that the resistivity is governed by disorder-induced band broadening in momentum space rather than by local density-of-states effects, providing a unified microscopic interpretation of the breakdown of Linde's rule in Cu-based alloys.
Read the full abstract

Materials Science · Cross-listed from cond-mat.str-el

Dirac topology, anomalous Hall response, and giant magnetoresistance in carrier-compensated altermagnetic semimetal NiS

Shovan Gayen, Sk. Soyeb Ali and S K Panda

We combine first-principles density-functional theory, Berry-curvature analysis, semiclassical Boltzmann transport, and atomistic spin dynamics to establish hexagonal NiS as a compensated 3d altermagnetic semimetal in which topology, magnetism, and lattice dynamics are intrinsically intertwined. The rotational coset symmetry of the NiAs lattice produces momentum-dependent spin splitting characteristic of altermagnetism. With spin-orbit coupling, gapped Dirac-like crossings generate intense Berry-curvature hot spots and nearly compensated electron-hole pockets. This leads to a large and anisotropic intrinsic spin Hall conductivity comparable to that of several 4d, 5d metals, a symmetry-allowed anomalous Hall response despite zero net magnetization, and nonsaturating magnetoresistance exceeding 10000 percent. On the magnetic side, first-principles determination of the exchange tensor reveals dominant long-range superexchange and sizable anisotropic interactions, quantitatively reproducing the experimental Neel temperature. Our results identify NiS as a model 3d platform in which carrier compensation, altermagnetic symmetry, Berry-curvature driven transport, and lattice-sensitive magnetism coexist within a single symmetry framework, offering a design principle for multi-functional quantum responses in correlated transition-metal compounds.
Read the full abstract

Materials Science

Direct Imaging of Temperature Evolution of Polar Nanoregions and Chemically Ordered Regions in PMN Relaxor: Evidence for Polar Phase Percolation

Kohei Hino, Daisuke Morikawa, Desheng Fu et al. (+2 more)

Polar nanoregions (PNRs) are central to understanding the exceptional dielectric and piezoelectric properties of relaxor ferroelectrics and are key to advancing dielectrics for high-energy storage. However, direct real-space imaging of their formation and evolution remains a major challenge in condensed matter physics. Here, we report the real-space mappings of both PNRs and chemically ordered regions (CORs) in the prototypical relaxor Pb(Mg1/3Nb2/3)O3 and their temperature dependence using convergent-beam electron diffraction (CBED) combined with four-dimensional scanning transmission electron microscopy (4D-STEM). The results reveal that CORs, with sizes of 2-5 nm, remain static with temperature and act to suppress PNR growth. In contrast, PNRs evolve from isolated 2-5 nm regions at room temperature to interconnected structures ~10 nm in size at low temperatures, indicative of a percolation transition. These observations support the random-field model, in which PNRs emerge from a paraelectric matrix and their growth and collective interactions are constrained by random local fields associated with CORs.
Read the full abstract

All authors Kohei Hino, Daisuke Morikawa, Desheng Fu, Mitsuru Itoh, Kenji Tsuda

Tuesday 14 July

Materials Science · Cross-listed from cond-mat.soft

Fundamental Relation between Conductance of Biomolecules and the Fukui Function

Gabor Vattay

The finite-temperature conductance of a molecule coupled to metallic leads is derived entirely within the framework of density functional theory (DFT) and its time-dependent extension for open quantum systems. Starting from the Mermin grand potential, the foundational Kohn-Sham equations, the Fukui function, and the open-system master equation for the single-particle density matrix are systematically formulated. The non-equilibrium electron-phonon dissipator is obtained from the partial trace over the phonon bath. By applying Wick's theorem for non-interacting fermions, a fully exchange-symmetric collision integral is obtained that strictly preserves Pauli exclusion at the operator level. Performing a double perturbation expansion, initially in the applied voltage (linear response), and subsequently in the molecule-lead coupling (weak coupling), it is demonstrated that under the fast-thermalization condition, the complex exchange-correlation self-consistent field response is analytically projected out by the diagonal structure of the slow Liouvillian mode. Consequently, the thermal conductance is governed by the finite-temperature Fukui function, the central reactivity descriptor of conceptual density functional theory. This condition is satisfied in proteins, whose wave functions are extended and multifractal due to quantum criticality at the Anderson metal-insulator transition. This derivation establishes a fundamental link between electronic transport and chemical reactivity, identifying conducting paths with reactive sites. It opens new technological avenues connecting drug design to conductance experiments and also provides a foundation for designing next-generation bioelectronic sensing and computing architectures.
Read the full abstract

Materials Science · Cross-listed from quant-ph

Precision quantum simulation of magnon spectra and interactions

Trond I. Andersen, Nikita Astrakhantsev, Jeronimo Martinez et al. (+329 more)

Quantum simulation promises to advance materials discovery by accurately simulating complex states of matter, their microscopic excitations, and macroscopic response functions. The central challenge in resolving the underlying interacting dynamics is to combine high-fidelity evolution with the sophisticated control necessary to manipulate individual quasi-particles in quantum many-body states. Here, we report on high-precision simulation of both linear and non-linear response functions in a 2D XY spin-1/2 magnet using an analog-digital superconducting processor of up to 97 qubits. By interleaving digital gates with analog evolution precisely characterized via Hamiltonian learning, we selectively excite magnons at tunable energy densities. Measuring first the linear magnon response – a central probe in neutron-scattering experiments – we extract temperature-dependent spectra and lifetimes. Our results reveal stark variations in magnon decay rates across the Brillouin zone, with enhancement near van Hove singularities and suppression for edge-localized modes. Next, we perform a suite of nonlinear measurements, including the study of self-scattering mechanisms, as well as pump-probe spectroscopy to directly characterize the magnon interactions. While matrix-product state simulations capture the dynamics well in either small systems or at low temperatures, their predictions become inaccurate away from these limits. This work demonstrates precise simulation of the interacting dynamics in quantum magnets, and provides key insights into quasi-particles and their microscopic scattering mechanisms.
Read the full abstract

All authors Trond I. Andersen, Nikita Astrakhantsev, Jeronimo Martinez, Will Morong, Johannes Motruk, Dario Rossi, Brayden Ware, Bryce Kobrin, Weijie Wu, Elizabeth Bennewitz, Manuel Rudolph, Tom Westerhout, Amira Abbas, Rajeev Acharya, Laleh Aghababaie Beni, Ross Alcaraz, Sayra Alcaraz, Markus Ansmann, Frank Arute, Kunal Arya, Walt Askew, Juan Atalaya, Christopher Ayala, Ryan Babbush, Brian Ballard, Joseph Bardin, Hector Bates, Andreas Bengtsson, Majid Bigdeli Karimi, Alexander Bilmes, Simon Bilodeau, Felix Borjans, Alexandre Bourassa, Jenna Bovaird, Dylan Bowers, Leon Brill, Peter Brooks, Michael Broughton, David Browne, Brett Buchea, Bob Buckley, Tim Burger, Brian Burkett, Jamal Busnaina, Nicholas Bushnell, Jonas Bylander, Anthony Cabrera, Juan Campero, Hung-Shen Chang, Silas Chen, Zijun Chen, Ben Chiaro, Liang-Ying Chih, Agnetta Cleland, Bryan Cochrane, Matt Cockrell, Josh Cogan, Paul Conner, Tom Connolly, Harold Cook, Rodrigo Cortinas, William Courtney, Alexander Crook, Benjamin Curtin, Adam Dally, Sayan Das, Martin Damyanov, Dripto Debroy, Himadri Dey, Stijn de Graaf, Laura De Lorenzo, Sean Demura, Lucia De Rose, Agustin Di Paolo, Leon Ding, Howard Dobbs, Paul Donohoe, Ebru Dogan, Ilya Drozdov, Andrew Dunsworth, Rasmus Edholm, Valerie Ehimhen, Alec Eickbusch, Aviv Elbag, Lior Ella, Mahmoud Elzouka, David Enriquez, Catherine Erickson, Lara Faoro, Vinicius Ferreira, Marcos Flores, Leslie Flores Burgos, Sam Fontes, Ebrahim Forati, Jeremiah Ford, Brooks Foxen, Masaya Fukami, Alan Fung, Lenny Fuste, Suhas Ganjam, Gonzalo Garcia, Christopher Garrick, Robert Gasca, Helge Gehring, Robert Geiger, Élie Genois, William Giang, Dar Gilboa, James Goeders, Edward Gonzales, Raja Gosula, Alejandro Grajales Dau, Dietrich Graumann, Joel Grebel, Alex Greene, Jonathan Gross, Jose Guerrero, Tan Ha., Steve Habegger, Tanner Hadick, Ali Hadjikhani, Michael Hamilton, Monica Hansen, Matthew Harrigan, Sean Harrington, Jeanne Hartshorn, Stephen Heslin, Paula Heu, Oscar Higgott, Reno Hiltermann, Jeremy Hilton, Hsin-Yuan Huang, Michael Hucka, Christopher Hudspeth, Ashley Huff, William Huggins, Aditya Jayaraman, Evan Jeffrey, Shaun Jevons, Zhang Jiang, Xiaoxuan Jin, Cody Jones, Chaitali Joshi, Kelsey Josund, Pavol Juhas, Andreas Kabel, Bharath Kannan, Hui Kang, Kiseo Kang, Amir Karamlou, Ryan Kaufman, Tanuj Khattar, Mostafa Khezri, Seon Kim, Paul Klimov, Can Knaut, Alexander Korotkov, Fedor Kostritsa, John Mark Kreikebaum, Ryuho Kudo, Arun Kumar, Ben Kueffler, Vladislav Kurilovich, Vitali Kutsko, Nathan Lacroix, Tiano Lange-Dei, Brandon Langley, Pavel Laptev, Kim-Ming Lau, Emma Leavell, Loïck Le Guevel, Justin Ledford, Joy Lee, Kenny Lee, Brian Lester, Wendy Leung, Matthew Lloyd, Lily Li, Wing Li, Ming Li, Alexander Lill, Mike Lindmark, William Livingston, Aditya Locharla, Erik Lucero, Daniel Lundahl, Aaron Lunt, Sid Madhuk, Donald Macaskill, Aniket Maiti, Ashley Maloney, Salvatore Mandra, Leigh Martin, Orion Martin, Eric Mascot, Paul Masih Das, Anselme Massimino, Melvin Mathews, Cameron Maxfield, Jarrod McClean, Matthew McEwen, Seneca Meeks, Anthony Megrant, Tim Menke, Kevin Miao, Zlatko Minev, Reza Molavi, Sebastian Molina, Shirin Montazeri, Akira Nakamura, Charles Neill, Konstantin Nesterov, Michael Newman, Roselle Ngaloy, Anthony Nguyen, Murray Nguyen, Chia-Hung Ni, Murphy Niu, Nicholas Noll, Sergey Novikov, Logan Oas, Ricky Oliver, Will Oliver, Raymond Orosco, Kristoffer Ottosson, Alice Pagano, Manan Patel, Sherman Peek, David Peterson, Alex Pizzuto, Thomas Plumb-Reyes, Elias Portoles, Rebecca Potter, Orion Pritchard, Sam Probst, Michael Qian, Chris Quintana, Matthew Rakher, Arpit Ranadive, Ganesh Ramachandran, Armin Razavi, Matthew Reagor, Rachel Resnick, David Rhodes, Daniel Riley, Gabrielle Roberts, Roberto Rodriguez, Emma Ropes, Eliott Rosenberg, Emma Rosenfeld, Dario Rosenstock, Elizabeth Rossi, Pedram Roushan, David Rower, Robert Salazar, Kannan Sankaragomathi, Murat Sarihan, Kevin Satzinger, Max Schaefer, Sebastian Schroeder, Henry Schurkus, Aria Shahingohar, Michael Shearn, Aaron Shorter, Shvarts Vladimir, Vlad Sivak, Spencer Small, W. Clarke Smith, David Sobel, Barrett Spells, Sofia Springer, George Sterling, Scott Stonemeyer, John Su, Jordan Suchard, Youngkyu Sung, Aaron Szasz, Alex Sztein, Tomoyuki Tanaka, Madeline Taylor, Jothi Thiruraman, Douglas Thor, Brandur Thorgrimsson, Dogan Timucin, Eifu Tomita, Alfredo Torres, M. Mert Torunbalci, Hao Tran, Abeer Vaishnav, Justin Vargas, Gopinath Vasalamarri, Sergey Vdovichev, Guifre Vidal, Benjamin Villalonga, Meghan Voorhees, Steven Waltman, Jonathan Waltz, Shannon Wang, Danni Wang, James Watson, Yonghua Wei, Travis Weidel, Theodore White, Kristi Wong, Bryan Woo, Christopher Wood, Maddy Woodson, Cheng Xing, Z. Jamie Yao, Ping Yeh, Bicheng Ying, Juhwan Yoo, Noureldin Yosri, Elliot Young, Grayson Young, Adam Zalcman, Ran Zhang, Yaxing Zhang, Yiqing Zhou, Ningfeng Zhu, Nicholas Zobrist, Zhenjie Zou, Sergio Boixo, Yu Chen, Julian Kelly, Hartmut Neven, Vadim Smelyanskiy, Dvir Kafri, L. B. Ioffe, Kostyantyn Kechedzhi, Xiao Mi, Dmitry Abanin

Materials Science · Cross-listed from cond-mat.mes-hall

Electronic properties and topological aspects of graphene nanohelicoids

Xiaoqian Liu, Arsen Herasymchuk, Yaroslav Zhumagulov et al. (+1 more)

We introduce graphene nanohelicoids, geometric analogues of graphene nanoribbons, in which the honeycomb lattice is embedded on a helicoidal surface. Starting from the three-dimensional helical structure, we construct effective one-dimensional lattice models with band structures characterized by a momentum-shifted particle-hole relation $E_v(k)=-E_c(k+\pi)$ that reflects an anti-chiral symmetry arising from the nonsymmorphic symmetry. A systematic investigation of graphene nanohelicoids using the tight-binding approximation reveals a number of trends upon varying width and edge orientation, for instance, alternating transitions between semiconducting and metallic regimes. As the structure width varies, the band gap periodically closes and reopens, accompanied by an alternating Zak phase that switches between trivial and nontrivial. We derive an analytic tight-binding model and introduce a continuous deformation of the graphene nanohelicoids that explains the origin of width-dependent band inversion and alternating Zak phase.
Read the full abstract

All authors Xiaoqian Liu, Arsen Herasymchuk, Yaroslav Zhumagulov, Oleg V. Yazyev

Materials Science

Multiwavelength Raman investigation of mono- and few-layer MoS2 grown by Pulsed Laser Deposition on SiO2

Alice Cartoceti, Paolo D'Agosta, Francesco Tumino et al. (+3 more)

Molybdenum disulfide (MoS$_2$) is a semiconductor whose vibrational and excitonic properties are highly sensitive to layer number and structural disorder. We demonstrate the growth of MoS$_2$ monolayers on inert, electronics-compatible SiO$_2$ substrates using room-temperature pulsed laser deposition (PLD). Control of the process parameters enables tuning from monolayer to multilayer films, which we investigate by multiwavelength Raman spectroscopy. The evolution of the Raman-shift difference between the $E_{2g}^{1}$ and $A_{1g}$ modes, combined with an assessment of defect density, tracks film growth as a function of the number of deposition laser pulses. Although excitonic effects strongly influence the optical response of two-dimensional transition-metal dichalcogenides, experimental reports of symmetry-selective exciton-phonon coupling remain limited. We provide experimental evidence of symmetry-dependent exciton-phonon coupling in PLD-grown monolayer MoS$_2$. Specifically, we observe modulation of the resonant behaviour of the out-of-plane $A_{1g}$ and in-plane $E_{2g}^{1}$ modes, related to their different coupling to A excitons, predominantly derived from Mo $d_{z^2}$ orbitals, and C excitons, characterized by mixed orbital contributions from Mo $d_{z^2}$ and S $p_x$ and $p_y$ states. Comparison with mechanically exfoliated monolayers reveals the role of growth-induced defects in modulating these interactions. These findings establish room-temperature PLD as a viable approach for growing two-dimensional MoS$_2$ on inert, electronics-compatible substrates and provide insight into the interplay between excitonic resonances and growth-induced disorder in two-dimensional MoS$_2$.
Read the full abstract

All authors Alice Cartoceti, Paolo D'Agosta, Francesco Tumino, Valeria Russo, Carlo S. Casari, Andrea Li Bassi

Materials Science

Synthesis of the Elusive Bulk Iodide Double-Perovskite Semiconductor, Cs2AgBiI6: Microcrystals and Photoconductive Films

Faris Horani, Nicolas Nguyen, Carmelita Ro-Mendez et al. (+2 more)

Three-dimensional (3D) iodide double-perovskite (elpasolite) semiconductors have attracted interest as potential lead-free metal-halide absorber layers for solar applications. Although studied extensively by computational methods, they have remained largely inaccessible synthetically, consistent with their predicted thermodynamic instability. Here, we report the first synthesis of bulk Cs2AgBiI6, demonstrating both microcrystalline and thin-film forms. Microcrystalline powders of Cs2AgBiI6 were prepared via anion exchange from phase-pure Cs2AgBiBr6 microcrystals. The resulting iodide elpasolite shows broad absorption throughout the visible with a 1.70 +/- 0.05 eV optical bandgap and near-infrared photoluminescence centered at 1.03 eV. We identify the elimination of trace moisture in bulk Cs2AgBiBr6 as the critical factor enabling complete halide exchange and isolation of bulk Cs2AgBiI6 with phase purity. In inert atmosphere, microcrystalline Cs2AgBiI6 shows no decomposition when stored for months at room temperature or heated to ~70 {\deg}C, and it appears equally stable in dry air. Building upon these insights, we then demonstrate the preparation of phase-pure Cs2AgBiI6 films by flash thermal evaporation of Cs2AgBiBr6 followed by anion exchange. Photoconductivity measurements on such Cs2AgBiI6 films demonstrate photocarrier generation and transport, marking the first optoelectronic measurement on this elusive 3D iodide double perovskite.
Read the full abstract

All authors Faris Horani, Nicolas Nguyen, Carmelita Ro-Mendez, Nicholas J. Adams, Daniel R. Gamelin

Materials Science · Cross-listed from cond-mat.str-el

Three-Dimensional Non-Foliated Fractional Quantum Hall Phases with Irrational Anyons in Twisted van der Waals Multilayers

Seyoung Jin, Hyeonseo Lim, Youngwook Kim et al. (+1 more)

Three-dimensional fractional quantum Hall phases offer a route to intrinsically higher-dimensional topological order beyond simple stacks of two-dimensional quantum Hall liquids. Such phases can exhibit non-foliated, intrinsically three-dimensional entanglement structures, exponentially large topological degeneracies and quasiparticles with irrational braiding statistics. Their microscopic realization has remained elusive because Landau quantization in three dimensions generally leaves dispersive one-dimensional bands, favoring metallic and density-wave states over incompressible fractional liquids. Here we show that large-angle twisted van der Waals multilayers provide a practical route around this obstruction. Large twist angles suppress coherent interlayer tunneling through momentum mismatch, while the atomic-scale layer separation preserves strong interlayer Coulomb interactions. Using Monte Carlo calculations to compare the energies of an extensive set of 862 competing trial wavefunctions, we find that generalized Halperin states with quantum coherence extending across multiple consecutive layers are stabilized. In experimentally accessible magnetic-field regimes, these states replace the metallic spontaneous-interlayer-coherent phases that dominate conventional untwisted graphite-like multilayers. The resulting liquids realize non-foliated fractional quantum Hall order closely related to fractonic topological order, hosting quasiparticles with rational electric charges but irrational braiding statistics. Their large topological degeneracy and non-rational statistical phases may offer unconventional resources for quantum information storage and processing. Our results establish twisted van der Waals multilayers as a realistic materials platform for three-dimensional fractional Hall matter beyond conventional two-dimensional quantum Hall systems.
Read the full abstract

All authors Seyoung Jin, Hyeonseo Lim, Youngwook Kim, Gil Young Cho

Materials Science

DeepCormack: Fermi surface tomography using model-based data-driven algorithms

Georg F. B. Lovric, Bryn Drury, Carola-Bibiane Schönlieb et al. (+2 more)

The experimental reconstruction of the 3D two-photon momentum density (TPMD) via angular correlation of electron-positron annihilation radiation (ACAR) is a particularly useful method for studying material Fermi surfaces. It does not rely on low temperatures, UHV conditions, or strong magnetic fields, and enables the study of the spin-resolved electronic structure of materials. Yet, it remains a challenging inverse problem. Typically, 10^8 positron annihilation events are measured for 3–6 projections of the TPMD at different angles. The standard reconstruction approach is an ACAR adaptation of Cormack's method (the MCM) that leverages the inherent symmetry in the crystal's structure. However, the poor signal-to-noise ratio means collecting data of sufficient quality for Fermi surface studies can take months per sample. We present DeepCormack, a family of data-driven model-based reconstruction algorithms that augments the MCM by integrating supervised deep-learning models (CNN, MLP, and UNet) at various stages. To overcome the lack of large experimental training sets, we propose a method which leverages singular value decomposition with dynamic mode decomposition to generate realistic synthetic TPMD volumes, requiring only a single reference momentum density computed via density functional theory. On test data, DeepCormack improves reconstruction quality over MCM by about 8.5 dB PSNR at 200M counts and remains stable at reduced counts, enabling significantly faster acquisition times. Generalisation to experimental data depends strongly on how well the training distribution from the reference momentum density matches the sample. We therefore recommend pairing DeepCormack with a DFT calculation of the target material to create sample-specific training data. Our proposed method offers either much higher quality reconstructions, or enables significantly faster ones, on the order of weeks.
Read the full abstract

All authors Georg F. B. Lovric, Bryn Drury, Carola-Bibiane Schönlieb, Stephen B. Dugdale, Ander Biguri

Materials Science

Surface Phase-Field-Crystal-Helfrich model for out-of-plane deformations in thin crystalline sheets with lattice mismatch

Emma Radice, Ingo Nitschke, Marco Salvalaglio et al. (+1 more)

Thin, flexible crystalline sheets exhibit unique elastic properties due to their ability to undergo out-of-plane deformations. Understanding this behavior requires a description that couples in-plane elasticity, out-of-plane deformation, and their coupling, taking the crystalline structure and its defects into account. We develop a multiscale description for these systems by extending the surface Phase-Field-Crystal-Helfrich model. The extension permits a spatially varying equilibrium lattice spacing, enabling the representation of localized lattice eigenstrain to mimic lattice mismatch in heterostructures. We validate the extended model against analytical predictions from classical Föppl-von Kármán equations for uniaxial compression and from Eshelby's inclusion problem. Using this validated framework, we then show how locally induced compressive stresses drive out-of-plane deformation in the sheets.
Read the full abstract

All authors Emma Radice, Ingo Nitschke, Marco Salvalaglio, Axel Voigt

Materials Science

Decoupling Strain-Rate Sensitivity and Deformation Length Scale Effects in Neutron-Irradiated Tungsten: A Coupled Nano-Indentation, HR-EBSD and Crystal Plasticity Study

Prashil S. Joshi, Bethany Jim, Chris Hardie et al. (+3 more)

Plastic deformation during strain-rate-controlled spherical nanoindentation is governed by the coupled evolution of constitutive strain-rate sensitivity and deformation length scale, making the intrinsic influence of strain rate difficult to isolate experimentally. This coupling is investigated in unirradiated and neutron-irradiated single-crystal tungsten using spherical nanoindentation, atomic force microscopy, high-resolution electron backscatter diffraction (HR-EBSD), and crystal plasticity finite element (CPFE) modeling. Nanoindentation experiments were performed at strain rates from 3.2e-5 to 3.2e-3 per second. AFM and HR-EBSD quantified surface pile-up, residual lattice strain, and geometrically necessary dislocation (GND) distributions. A strain-gradient CPFE framework incorporating thermally activated slip, GND hardening, irradiation-induced obstacle hardening, and strain-dependent softening was calibrated using a single experimental condition and validated across all remaining strain rates without further parameter adjustment. The validated model was then used to independently vary strain rate and indentation depth. Simulations show that strain rate primarily controls the stress required for thermally activated plastic flow, whereas indentation depth governs plastic-zone evolution, pile-up, and GND accumulation. Irradiation increases obstacle strength and promotes deformation localization while remaining consistent with a common thermally activated mechanism. The framework also predicts the compression response of a polycrystalline cube, demonstrating transferability across loading conditions and length scales, providing a robust basis for constitutive modeling of irradiation-hardened materials under transient loading.
Read the full abstract

All authors Prashil S. Joshi, Bethany Jim, Chris Hardie, Angus Wilkinson, David EJ Armstrong, Suchandrima Das

Materials Science · Cross-listed from cond-mat.str-el

Phase-shifted multicomponent spin-charge nematicity in an altermagnet

Christopher Candelora, Siyu Cheng, Muxian Xu et al. (+7 more)

Altermagnets host spin-split Fermi surfaces without net magnetization. This intrinsically multicomponent electronic setting raises the possibility that familiar correlated electron phases acquire unconventional spin-charge structure. Here we report the discovery of altermagnetic nematicity in Co0.25NbSe2. Using spectroscopic-imaging scanning tunneling microscopy and spin-polarized scanning tunneling microscopy, we find that the three nominally C3-related directions lose rotational equivalence in the zero-field state, in both charge and spin-sensitive tunneling channels. Strikingly, the dominant spin-sensitive component is shifted by one C3 sector relative to the dominant charge component, revealing a phase-shifted spin-charge nematic response. A phenomenological theory shows that altermagnetic order favors a finite relative phase between the charge and spin-sensitive nematic components – C3 lattice pinning frustrates this preferred offset and selects the observed phase locking. These results establish altermagnetic nematicity as a new form of multicomponent electronic liquid-crystal order and point to a potentially generic route by which altermagnets can transform conventional correlated phases into symmetry-engineered spin-charge orders.
Read the full abstract

All authors Christopher Candelora, Siyu Cheng, Muxian Xu, Keyu Zeng, Hengxin Tan, Younghun Hwang, Binghai Yan, Federico Mazzola, Ziqiang Wang, Ilija Zeljkovic

Materials Science · Cross-listed from physics.optics

Symmetry-Informed Deep Learning for Electromagnetic Scattering

Viktor A. Lilja and Philippe Tassin

Deep learning can accelerate the modeling of electromagnetic devices by replacing costly simulations with neural networks trained to map design parameters to scattering parameters. However, data efficiency remains a central bottleneck, as training data is typically generated through expensive numerical simulations. Here we show that symmetry provides a powerful and largely untapped route to overcoming this limitation in electromagnetic scattering problems. Leveraging the equivariance of Maxwell's equations, we obtain general transformation rules that map symmetries of electromagnetic devices to corresponding transformations of their scattering parameters. This enables both systematic data augmentation and the construction of exactly equivariant neural networks. We implement the framework for both discrete and continuous symmetry groups and demonstrate its effectiveness on photonic-crystal slabs and free-form diffraction gratings. Incorporating symmetry improves data efficiency by an order of magnitude compared to standard architectures, while equivariant models additionally enforce physical constraints exactly. Our approach is general and complementary to existing physics-informed strategies, provides a first-principles framework for constructing physically grounded surrogate models, and establishes symmetry as a unifying inductive bias for data-efficient and physically consistent learning in computational electromagnetics and beyond.
Read the full abstract

Materials Science

Single-orbital tight-binding model for chiral one-dimensional hybrid organic-inorganic lead halide perovskites

Yuya Ominato, Tetsuya Furukawa, Ayumi Ishii et al. (+1 more)

We present a single-orbital tight-binding model for the low-energy electronic states of the chiral one-dimensional hybrid organic-inorganic lead halide perovskite $\mathrm{(}R/S\mathrm{-PEA)PbI}_3$. The model is constructed from a single effective orbital on each of the four symmetry-related sites in the primitive unit cell and incorporates layer, in-plane sublattice, and spin degrees of freedom. With separate parameter sets for the conduction and valence bands, the effective Hamiltonian reproduces the overall band dispersions obtained from density-functional-theory calculations and quantitatively captures the spin splittings near the band edges. It also captures the leading spin-polarization patterns of the Bloch states, showing that the band-edge spin splitting and spin polarization are encoded in a small number of symmetry-adapted spin-dependent hopping terms. We further analyze the accidental degeneracies of the effective Hamiltonian using screw eigenvalues and antiunitary operators. This analysis separates accidental degeneracies originating from the restricted term content of the effective Hamiltonian from degeneracies enforced by nonsymmorphic screw symmetries and time-reversal symmetry. The present model provides a symmetry-transparent starting point for understanding the band-edge electronic structure of chiral lead halide perovskites and for analyzing optical, spin, and transport responses in this class of materials.
Read the full abstract

All authors Yuya Ominato, Tetsuya Furukawa, Ayumi Ishii, Tetsuaki Itou

Materials Science

Strain-Tunable Shift Current and Magneto-Optical Kerr Effect in Multiferroic Altermagnet Fe2Mo3O8

Shengqiao Wang, Bo Zhao, Harish K. Singh et al. (+6 more)

Altermagnetism has recently emerged as a compelling frontier in spintronics, seamlessly merging the agile tunability of ferromagnets with the hallmark merits of antiferromagnets. As a prototypical polar multiferroic featuring distinctive altermagnetism, Fe2Mo3O8 hosts an ideal playground for exploring the intricate interplay among ferroelectric polarization, altermagnetic order, and spin-dependent responses. Here, employing first-principles calculations, we systematically investigate the coupling among polarization, spin splitting, shift current, and magneto-optical responses in Fe2Mo3O8. Our findings reveal that switching the ferroelectric polarization not only inverts the sign of the shift current but also comprehensively reshapes the momentum-space spin-splitting texture. Furthermore, the shift current and magneto-optical spectrum exhibits strong tunability under mechanical strain. Remarkably, the application of a-axis uniaxial strain breaks the crystalline symmetry, thereby activating a finite magneto-optical Kerr effect that is otherwise forbidden in the pristine phase.
Read the full abstract

All authors Shengqiao Wang, Bo Zhao, Harish K. Singh, Jiahao Xie, Fu Li, Hongbin Zhang, Yang Su, Chen Shen, Lijun Zhang

Materials Science

Photogeneration and signatures of coherent phonons in time-resolved photoemission spectroscopy: First-principles time-dependent adiabatic GW approach

Yang-hao Chan, Zhenglu Li and Steven G. Louie

Coherent lattice dynamics can be observed in pump-probe time-resolved and angle-resolved photoemission spectroscopy (TR-ARPES) as a periodic modulation of intensity and energy of photoelectrons over probe time. We present an ab initio time-dependent GW approach including electron-phonon (e-ph) couplings to simulate the photogeneration of coherent phonons and their effects on the TR-ARPES of monolayer MoS2. We demonstrate that state-resolved e-ph coupling strength can be obtained from analyzing coherent phonon modulations on TR-ARPES. Features of both the impulsive stimulated Raman scattering mechanism and the displacive excitation mechanism of coherent phonon generation are identified in our simulations. We clarify their origins and the coincident selection rule of coherent phonon generation and Raman scattering intensity. This method provides supports to analyze coherent phonon dynamics and e-ph couplings in TR-ARPES and enables quantitative engineering of band structure through coherent phonons.
Read the full abstract