Materials Science
First-Principles Study of Novel Lead-Free Double Perovskite e̱ta}2SnGeX6 (e̱ta} = K, Rb; X = Cl, Br, I) for thermomechanical, optoelectronic and outstanding thermoelectric applications
Jubair Hossan Abir, Tauhidur Rahman, S.S.B. Pallab et al. (+3 more)
In this study, the structural, mechanical, electronic, optical, and thermoelectric properties of the novel lead-free halide double perovskite series beta2SnGeX6 (beta = K, Rb; X = Cl, Br, I) are systematically investigated using density functional theory (DFT). Calculated formation energies, Tolerance factors, and octahedral factors confirm that all six compounds exhibit robust thermodynamic stability within a highly symmetric cubic geometry. Mechanical analysis derived from elastic parameters characterizes the entire series as fundamentally ductile, ensuring high processing elasticity and resistance to micro-cracking during device manufacturing. Electronic band structures reveal direct bandgaps showing exceptional composition-dependent tunability from 1.44 eV down to 0.64 eV via progressive halogen substitution. The wide gap chloride variations are optimized for single-junction photovoltaic absorbers, while the narrower-gap bromide and iodide analogs show immense promise for tandem
solar architectures and near-infrared photodetectors. Thermoelectrically, heavy constituent atoms introduce strong
lattice anharmonicity and intense high-temperature Umklapp
phonon scattering, significantly suppressing
lattice thermal conductivity. Combined with low carrier effective masses that optimize electrical transport, the iodide compounds achieve higher power factors and outstanding dimensionless figures of merit (ZT = 2.4 for K2SnGeI6 at 1000 K). Ultimately, these lead-free double perovskite family emerges as an environmentally benign and versatile platform for next-generation green optoelectronics and solid-state waste-heat recovery.
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All authors Jubair Hossan Abir, Tauhidur Rahman, S.S.B. Pallab, Md. Sharear Aman, R. S. Islam, S. H. Naqib
Statistical Mechanics
Thermodynamics of photonic nonlinear Aharonov-Bohm cages
Stefano Iubini and Carlo Danieli
We investigate
equilibrium and non-
equilibrium thermodynamics of one-dimensional photonic diamond
lattices with Kerr nonlinearity. The
equilibrium phase diagram is obtained as a function of the synthetic
magnetic flux acting on each plaquette. In the linear regime, the
magnetic flux can induce Aharonov-Bohm caging, flattening all Bloch bands and suppressing particle and energy currents. In this caging regime, non-vanishing currents are enabled by nonlinearity. By imposing stationary temperature- and chemical potential- imbalances at the system boundaries, we show that at weak nonlinearity fine tuning the flux at the Aharonov-Bohm caging transforms the system from a conductor to an
insulator. For intermediate nonlinear strength, the system remains conducting for all
magnetic fluxes; however, the caging condition significantly enhances the Seebeck coefficient and thermoelectric figure of merit, improving the thermoelectric features of the system. Our results give evidence of a novel route towards optimization of coupled transport devices, based on the control of linear versus nonlinear conduction channels via a synthetic
magnetic flux.
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Mesoscale and Nanoscale Physics
Theory of In-Plane Orbital Magnetization with Layer Hybridization
Jin-Xin Hu, Zi-Ting Sun and Yugui Yao
The modern theory of orbital magnetization successfully describes the response of Bloch electrons to
magnetic fields in fully periodic
crystals, but it does not directly address the distinct regime of an in-plane field in multilayer systems with layer hybridization. Coherent interlayer tunneling allows electrons to form circulating current loops, producing an in-plane orbital response that is absent in a strictly two-dimensional limit and qualitatively different from the conventional three-dimensional one. Here we develop a theory of in-plane orbital magnetization for this transdimensional regime, where the layer thickness is comparable to the vertical mean free path. Starting from the current-loop picture, we construct the in-plane orbital angular momentum operator and derive exact expressions for the orbital
magnetic moment and the in-plane orbital
magnetic susceptibility. As an application, we predict a gate-tunable in-plane orbital magnetoelectric effect in layered materials. Our framework establishes a general foundation for in-plane orbital responses and suggests new opportunities for orbitronics in layer-hybridized
quantum materials.
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Soft Condensed Matter
On the emergence of molecular tilt in a ferroelectric smectic liquid crystal with broken director-inversion symmetry
Aitor Erkoreka, Mauricio Vera-Arévalo, Alberto Concellón et al. (+5 more)
The origin of some mesophases of the ferroelectric nematic realm is not yet well understood. In this work we study the highly polar
liquid crystal MIO, a close structural analogue of the prototypical ferroelectric nematogen DIO, which exhibits a ferroelectric smectic A to ferroelectric smectic C (SmAF-SmCF) phase transition. Calorimetric, dielectric and light-scattering experiments reveal that it is a second-order phase transition with mean-field behavior, and is driven by the softening of the tilt elastic constant accompanied by the divergence of the amplitude of the associated dielectric mode.
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All authors Aitor Erkoreka, Mauricio Vera-Arévalo, Alberto Concellón, Sergio Diez-Berart, Jordi Sellarès, Adrià Gràcia-Condal, Ibon Alonso, Josu Martinez-Perdiguero
Mesoscale and Nanoscale Physics
Electron state tomography from quasiparticle interference maps
A. Razanajatovo, J. Cayssol and C. Dutreix
Characterizing electronic band structures requires precise knowledge of wave functions and their
quantum geometry. Here, we introduce a
tomography method to reconstruct the density
matrix of electron states from quasiparticle interference maps around single
impurities. We consider two-orbital models on a honeycomb
lattice, relevant to
graphene heterostructures and direct-gap
semiconductors. For on-site
impurities, backscattering between time-reversed states directly maps the density
matrix populations and coherences into distinct orbital contributions in the interference map. While local probes usually lack orbital resolution, these orbital contributions transform under distinct
symmetry group representations and can thus be disentangled to reveal the density
matrix and
quantum geometric tensor of the scattering states. This establishes
impurities as tomographic probes for band structures in scanning tunneling microscopy using conventional, unpolarized tips.
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Disordered Systems and Neural Networks
Extracting effective scaling exponents in finite-size hyperuniform systems
Yuan Liu, Xurui Li, Jianxiang Tian et al. (+2 more)
Hyperuniform systems strongly suppress long-wavelength density fluctuations, which is quantitatively characterized by the small-wavenumber scaling. In finite samples, however, accurately estimating the hyperuniformity exponent {\alpha} can be challenging. The inferred value depends strongly on the range of length scales accessible in the measurement, finite-size effects, and the specific characterization method employed, whether based on
Fourier-space structure factors, real-space density fluctuations, or dynamical probes such as
diffusion spreadability. In particular, the structure-factor method provides the most direct estimate of {\alpha}, but is sensitive to empirical low-k fitting cutoffs. The number-variance method offers a real-space Class-like diagnosis, but contributes a numerical exponent only when the finite-size data retain Class III-like scaling information. The spreadability method provides a smoother dynamic estimate and reduces configuration-level fluctuations, but requires a physically admissible long-time fitting window. Here, we develop a practical method-aware protocol for robust estimation of the effective scaling exponent {\alpha} in finite-size hyperuniform point configurations, combining three complementary methods with distinct roles. Our protocol summarizes the method-specific estimates through a joint empirical
estimator and reports the internal dispersion among the participating methods to determine the optimal estimate.
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All authors Yuan Liu, Xurui Li, Jianxiang Tian, Xunwang Yan, Ge Zhang
Statistical Mechanics
Classical dissipative search of unstructured database
A.E. Allahverdyan and Y. Bisharyan
We propose a physical realization of the unstructured database search that works via classical, dissipative model of spherical
spins. The database is implemented via
spin-
spin couplings, where the selected coupling refers to a larger
ferromagnetic interaction between two selected
spins. The low-temperature
equilibrium of this model leads to magnetization strongly concentrated on the selected
spins, which means that the search is complete. The search time refers to the relaxation time to
equilibrium from a homogeneous initial state, and is described via Langevin equations. This time scales as ${\cal O}(M^a)$ with $a<1/2$, where $M$ is the database volume. This is faster than Grover's search, showing how a dissipative, classical analog computer can overcome the
quantum unitary computer.
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Materials Science
Solution gate control of shallow silicon vacancy charge states in diamond
Charlie Pattinson, Daniel J. McCloskey, Nikolai Dontschuk et al. (+3 more)
Silicon-vacancy (SiV) centers in diamond combine near-infrared emission with solid-state robustness, but their performance hinges on isolating favorable defect charge states. We demonstrate static and dynamic control of ultra-shallow (<15 nm) SiV ensembles in type IIa diamond. By combining low-energy ion implantation with tailored oxygen and hydrogen terminations, we map regimes that maximise the fluorescent SiV- population over dark charge states. We then realize reversible SiV- to SiV0 conversion using aqueous electrolytic gating with sub-200 mV biases and low optical powers. Our results enable low-power electrical control of SiV ensembles for integrated
quantum photonics and biologically compatible voltage imaging in the near-infrared.
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All authors Charlie Pattinson, Daniel J. McCloskey, Nikolai Dontschuk, Brett C. Johnson, Alexander A. Wood, David Simpson
Strongly Correlated Electrons
Mimicry of chaos and $k$-design in higher order OTOCs of Luttinger liquids
Balázs Dóra, Catalin Pascu Moca and Roderich Moessner
Out-of-time-order correlators (OTOCs) provide a fundamental metric for
quantum chaos, but capturing the fine structure of information scrambling requires exploring their higher-order generalizations. Here, we systematically investigate the sequence of higher-order OTOCs in a Luttinger
liquid and its
lattice realization, the XXZ Heisenberg chain. Using bosonization and numerics, we extract the full temporal dynamics of the first three OTOCs, revealing that they rapidly erase
memory of the initial state, and quickly saturate to their steady state values. Strikingly, we show that calculating the late time saturation values for the entire sequence of higher-order OTOCs maps exactly onto determining the partition function of a non-Hermitian Harper model. Through this mapping, we demonstrate that for moderately strong interactions, the steady-state OTOCs become parametrically small up to the seventh order, mimicking higher $k$-design. Our results reveal that Luttinger
liquids exhibit an unexpectedly profound degree of apparent scrambling when viewed through the lens of higher-order OTOCs.
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Mesoscale and Nanoscale Physics
Polarized neutron scattering as a probe for vortex-type spin correlations in iron oxide multicore assemblies
Venus Rai, Ivan Titov, Elizabeth M. Jefremovas et al. (+11 more)
We report an experimental investigation of the
magnetic microstructure of iron
oxide multicore assemblies by means of polarized small-angle
neutron scattering (SANS). Guided by a recently developed analytical theory for
vortex-state
magnetic nanoparticles, we provide a quantitative comparison between the measured and calculated cross sections, revealing signatures that are consistent with
vortex-type magnetization configurations at low applied
magnetic fields. In particular, the field
evolution and the characteristic isotropic ring-type feature of the
spin-flip scattering intensity at intermediate momentum transfers are in line with the formation of flux-closure states. The latter are stabilized by the interplay of exchange, Zeeman, and magnetostatic energies. The methodology allows for a statistically significant characterization of
vortex states in densely packed nanoparticle systems, thereby complementing surface-sensitive techniques that are commonly limited to the observation of
spin structures in individual particles.
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All authors Venus Rai, Ivan Titov, Elizabeth M. Jefremovas, Štefan Liščák, Sivarenjini Shan, Nina-Juliane Steinke, Jonathan Leliaert, Álvaro Gallo-Córdova, María P. Morales, Davide Peddis, Pierfrancesco Maltoni, Luis Fernández Barquín, Andreas Michels, Michael P. Adams
Strongly Correlated Electrons · Cross-listed from hep-th
Hydrodynamics of perfect fluids with anomalies from the fermionic path integral
Alexander G. Abanov and Andrea Cappelli
The path integral of the Dirac
fermion with vector and axial gauge backgrounds is analyzed near the infrared limit in the presence of residual irrelevant current-current interaction. After integrating out
fermions, a semiclassical low-energy effective action is obtained, written in terms of currents. Its expression is found to correspond to the hydrodynamic action previously proposed for perfect barotropic fluids with anomalies at zero temperature. This approach also leads to two further hydrodynamic actions to be associated, respectively, with the Weyl
fermion, and the Dirac
fermion having independent vector and axial currents. These actions feature four- and five-dimensional bulk-boundary terms, owing to anomaly inflow, which are identified as being the so-called transgression forms. These are generalizations of Chern–Simons forms that involve two gauge fields: the dynamical field and the background field. The path-integral argument provides a “microscopic” explanation for several ingredients of the action formulation of hydrodynamics that are necessary to incorporate anomalies. It also clarifies the infrared reduction required to pass from the effective field theory to a local hydrodynamic description. This reduction is implemented by considering restricted variations of the action, familiar from hydrodynamics, which at the same time lead to four-dimensional equations of motion from the five-dimensional transgression terms.
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Materials Science
Role of Local Structural Variation in X-ray Photoelectron Spectrum of Silicon Oxide Interfaces
Mikael Santonen, Sari Granroth, Johanna Laaksonen et al. (+2 more)
We show that the broad X-ray photoelectron lines of silicon
oxide on silicon arise from a continuous statistical distribution of core-level binding energies. Statistical simulations spanning compositions from Si to SiO$_2$ reproduce the full extent of this broadening, reaching 5 eV for SiO$_{1.0}$ , in quantitative agreement with 0.23 nm layer-resolved spectra reconstructed from Ar$^+$ sputtering data. This continuous distribution blurs distinct spectral fingerprints of local structural motifs, thereby challenging conventional chemical state assignment in
oxide X-ray photoelectron spectra.
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All authors Mikael Santonen, Sari Granroth, Johanna Laaksonen, Pekka Laukkanen, Johannes Niskanen
Disordered Systems and Neural Networks · Cross-listed from math-ph
Self-averaging of replica overlaps in the random field Edwards-Anderson model
C. Itoi and Y. Sakamoto
The self-averaging of the replica overlap is proven in the Edwards-Anderson (EA) model under random field almost everywhere in the coupling constant space in any dimension. The EA order parameter is represented in terms of the derivative of the free energy density with respect to the random field strength, regardless of boundary conditions. Tasaki's correlation inequality for finite-dimensional
spin glass models shows that the expectation of the squared replica overlap is bounded by the squared EA order parameter. These simple evaluations enable us to prove that the variance of the replica overlap vanishes in the infinite-volume limit. The self-averaging of the replica bond overlap is proven also in the EA model with Gaussian exchange interaction without random field. Short-range
spin glass models have been shown to behave differently from mean-field
spin glass models with RSB phase.
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Soft Condensed Matter
Ewald summing irreducible components of flow around active particles
Mayurakshi Deb and Rajesh Singh
We present a method to compute Ewald summation for the irreducible components of flow around active particles to study hydrodynamic interactions in active colloidal suspensions. An active particle is modeled as a colloidal sphere with a surface slip velocity. Using this model, we obtain an irreducible representation of the fluid flow produced by an active particle in periodic geometry of Stokes flow for an arbitrary surface slip. The solution of the active flow is obtained in terms of
lattice sum of the Oseen tensor and their derivatives. The
lattice sum is accelerated using the Ewald summation technique. We apply the method to compute explicit expression for rigid body motion of hydrodynamically interacting active particles. Our method presents a way for dynamic simulation of active particles due to arbitrary mode of active slip in periodic geometry of Stokes flow.
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Strongly Correlated Electrons
$d$-wave altermagnetism revealed by resonant inelastic X-ray scattering
Guangkai Zhang, Yuehong Li, Xubin Ye et al. (+16 more)
Altermagnetism defines a third fundamental class of collinear
magnetic order, featuring compensated
magnetic moments with antiparallel
spin alignment, yet lifted Kramers degeneracy without the need for relativistic
spin-orbit coupling. Its ability to host
spin-polarized electronic bands and unconventional
chiral magnons makes it a promising platform for functional materials. However, experimental verification has proven challenging; while circular dichroism in resonant inelastic X-ray scattering (RIXS) has been suggested as a signature of
chiral magnons, it remains controversial whether this effect is an intrinsic property of altermagnetism or an artifact of experimental geometry. In this work, we resolve this debate and provide unambiguous experimental evidence of $d$-wave altermagnetism in the strongly correlated Lieb-
lattice magnet La$_2$O$_3$Mn$_2$Se$_2$. The RIXS spectra exhibit a $d$-wave-
symmetry circular dichroism in the
magnetic excitations that vanishes in the paramagnetic phase. Through RIXS-operator
symmetry analysis and exact-diagonalization calculations, we prove that the observed dichroism is a direct consequence of altermagnetic
symmetry constraints, independent of
magnon branch splitting. Our results provide definitive evidence for the experimental realization of $d$-wave altermagnetism in La$_2$O$_3$Mn$_2$Se$_2$ and establish circularly polarized RIXS as a highly
symmetry-sensitive spectroscopic framework for detecting
magnetic phases that evade conventional probes.
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All authors Guangkai Zhang, Yuehong Li, Xubin Ye, Vincent C. Morano, Sze Tung Li, Jaewon Choi, Rebecca Scatena, Shuai Tang, Maocai Pi, Mengqi Ye, Mirian Garcia-Fernandez, Alessandro Bombardi, Xiaomei Qin, Zhao Pan, Daniel G. Mazzone, Qisi Wang, Yi Lu, Yao Shen, Youwen Long
Quantum Gases
Josephson spectroscopy in a circular atomic tunnel junction with acceleration-induced symmetry breaking
Yurii Borysenko, Yuriy Bidasyuk, Olena Prykhodko et al. (+5 more)
We study Josephson dynamics in a long atomic Bose-Josephson junction formed by two tunnel-coupled coplanar Bose-Einstein-condensate rings. An in-plane linear acceleration breaks the axial
symmetry of the trap and transforms a single Josephson
plasma oscillation into a multimode population-imbalance response. Gross-Pitaevskii simulations and Bogoliubov-de Gennes analysis show that the additional spectral components arise from collective modes that acquire finite overlap with the population-imbalance operator under
symmetry breaking, with their activation governed by reflection
symmetry about the acceleration direction. We also propose a mode-resolved Josephson-spectroscopy protocol based on a weak localized periodic perturbation. Frequency scans reveal resonant amplitude peaks and phase shifts at the eigenfrequencies of active Bogoliubov modes, while angular scans of the drive position provide access to the angular structure of the corresponding mode density perturbations. A dissipative time-dependent Bogoliubov theory yields analytical response functions in quantitative agreement with full Gross-Pitaevskii simulations in the linear regime. Our results demonstrate that accelerated dual-ring condensates provide a controllable platform for
symmetry-selected Josephson dynamics and spectroscopic probing of collective modes.
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All authors Yurii Borysenko, Yuriy Bidasyuk, Olena Prykhodko, Gerhard Birkl, Dominik Pfeiffer, Ludwig Lind, Mark Edwards, Alexander Yakimenko
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Attention as Frustrated Synchronization
Joshua Nunley
A network of oscillators that synchronizes perfectly computes nothing further, so an
attention architecture built from synchronization must locate its computation in structured departures from agreement. We introduce the Frustrated Synchronization Network (FSN), whose
token states are phases on a
torus and whose entire value pathway is one learned complex coupling kernel over harmonics and a one-step delay. Each component of the kernel is a frustration in the sense of the synchronization literature. The complex phases are static Kuramoto-Sakaguchi frustration angles, the signed harmonics are repulsive Daido components, and the delay term, which couples each
token to the successors of the
tokens it attends to, is algebraically identical to Kuramoto-Sakaguchi coupling whose frustration angle is the data's own transition, so next-
token prediction is implemented as synchronization frustrated by the data. At matched one-million-parameter and training budgets on character-level text and code, the FSN's validation loss is below a tuned RoPE-SwiGLU
transformer's at every epoch measured, and the comparison survives training the baseline to convergence: every thirty-epoch enwik8 seed finishes below the
transformer's converged fifty-epoch loss of 1.611, and the FSN's completed fifty-epoch runs converge to 1.5953 +/- 0.0014. A variant with every feed-forward block replaced by mean-field coupling to learned collective modes, leaving no multilayer perceptron in the stack, tracks the
transformer. On natural text the unfrustrated base layer falls behind the converged
transformer at every copy depth, worst on long-range copy events; the kernel reverses the deficit at every depth of four and beyond. Headline comparisons are at the one-million-parameter scale; a scale ladder is complete through four million parameters with the advantage persisting, and remaining arms are marked as in progress.
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Materials Science · Cross-listed from cs.LG
Robust and Interpretable Adaptation of Equivariant Materials Foundation Models via Sparsity-promoting Fine-tuning
Youngwoo Cho, Seunghoon Yi, Wooil Yang et al. (+6 more)
Pre-trained materials foundation models, or machine learning interatomic potentials, leverage general physicochemical knowledge to effectively approximate potential energy surfaces. However, they often require domain-specific calibration due to physicochemical diversity as well as mismatches between practical computational settings and those used in constructing the pre-training data. To address this, we propose a sparsity-promoting fine-tuning method that selectively updates model parameters by exploiting the structural properties of E(3)-equivariant materials foundation models. On energy and force prediction tasks across molecular and crystalline
benchmarks, our method matches or surpasses full fine-tuning and equivariant low-rank adaptation while updating only $\sim$3~% of parameters, and in some cases as little as $\sim$0.5~%. Beyond energy and force calibration, we further demonstrate task generalizability by applying our method to
magnetic moment prediction and magnetism-aware total energy modeling. Finally, analysis of sparsity patterns reveals physically interpretable signatures, such as enhanced $d$-orbital contributions in transition metal systems. Overall, our results establish sparsity-promoting fine-tuning as a flexible and interpretable method for domain specialization of equivariant materials foundation models.
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All authors Youngwoo Cho, Seunghoon Yi, Wooil Yang, Sungmo Kang, Young-woo Son, Jaegul Choo, Joonseok Lee, Soo Kyung Kim, Hongkee Yoon
Superconductivity
Counterintuitive inverse superconducting transition beyond 4He-cooling limit
Haowen Han, Yi Bian, Tong Ma et al. (+9 more)
Thermally driven
quantum-orders observed in exceptional instances may redefine the role of thermal-fluctuation from a source of decoherence to a resource for coherent-state engineering. While preliminary signs of counterintuitive temperature-rise-triggered superconductivity manifested in CeCu2Si2, ErRh4B4, Ho1.2Mo6S8 and (La,Ce)Al2, their critical-temperatures (Tc-inv) remain below Kelvin-range, precluding substantial applications. Here, we report field-modulated inverse-superconducting-transitions above 4He-cooling-limit in Eu-based infinite-layer nickelates (EuxNd1-xNiO2 and EuxPr1-xNiO2) grown on a substrate under both overdoped and underdoped regimes. Paradigmatically, superconductivity with zero-resistance is confined between Tc-inv (2.6-5.4 K) and another higher normal-Tc, rising and decreasing with applied
magnetic-field, respectively. Starting from the resistive-state below Tc-inv, the inverse-superconducting-transition is driven by not only temperature-rising, but also current-density, while superconductivity further vanishes at higher temperature and current thresholds. The Kelvin-range inverse superconducting transition is plausibly explained by temperature-induced alternating dominance of effective
magnetic-fields arising from Eu2+4f7 related compensations relative to the upper-critical-field. Furthermore, an extended-phenomenological-framework is also supported by reemerged superconductivity below 300 mK under
magnetic-field, giving rise to an unprecedented temperature-induced reentrant superconductivity. Our findings establish
magnetic-interaction-reconfigured high-Tc systems as fertile platforms for exploring
quantum phenomena that reverse thermal-decoherence paradigm, also enabling antithetical-designs to unlock untapped application-scenarios for
quantum-phase-transition devices.
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All authors Haowen Han, Yi Bian, Tong Ma, Yusong Zhao, Nuofu Chen, Chuanying Xi, Ze Wang, Binghui Ge, Hongliang Dong, Jia-Cai Nie, Ho-Kwang Mao, Jikun Chen
Mesoscale and Nanoscale Physics
Bidirectional motion of antiferromagnetic skyrmions driven by competing spin torques
Laichuan Shen, Wang Kang, Xichao Zhang et al. (+4 more)
Antiferromagnetic skyrmions are swirling topological
spin textures with rich dynamics and intriguing transport properties, yet their bidirectional dynamics remain largely unexplored. Here, we investigate the dynamics of
antiferromagnetic skyrmions driven by current-induced
spin-transfer and
spin-orbit torques. We computationally demonstrate that
antiferromagnetic skyrmions moving in one direction at low current densities can reverse their motion direction when the driving current is above a threshold. Based on the Thiele approach analysis, we show that this bidirectional motion originates from a change in the relative strengths of two effective forces arising from
spin-transfer and
spin-orbit torques. Furthermore, exploiting this bidirectional motion on a single racetrack, we design programmable logic gates. Our results not only uncover a hidden mechanism for bidirectional skyrmion motion but also facilitate the development of antiferromagnet-based logic devices.
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All authors Laichuan Shen, Wang Kang, Xichao Zhang, Qiuping Huang, Yalin Lu, Zhifeng Zhu, Yan Zhou
Mesoscale and Nanoscale Physics
Trion Hall effect in electron-hole double layers
Raghav Chaturvedi, Phuong X. Nguyen, Patrick Knüppel et al. (+4 more)
The realization of Coulomb coupled electron-hole double layers in 2D
semiconductor heterostructures has enabled the thermodynamic and transport studies of
equilibrium exciton fluids without a
magnetic field. By doping the
exciton fluid with additional electrons/holes, an
equilibrium fluid of trions - three particle bound states of electrons and holes - further emerge, providing the platform to explore new transport phenomena associated with such composite particles. Here we report the observation of a
Hall effect for trions in MoSe2/WSe2 heterobilayers, which support Coulomb-coupled electron and hole fluids with tunable densities. The
Hall effect arises from a Lorentz force on trions under a perpendicular
magnetic field. It is manifested in both
Hall drag measurements and standard
Hall effect measurements on just one of the
semiconductor layers. For negatively charged trions, an electron
Hall effect is observed even in a hole doped WSe2 monolayer due to the presence of trion drags. The trion
Hall effect also disappears when the trions are ionized at elevated temperatures and/or high trion densities. Our work opens the door for realizing
quantum oscillations and the
quantum Hall effect for trions.
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All authors Raghav Chaturvedi, Phuong X. Nguyen, Patrick Knüppel, Kenji Watanabe, Takashi Taniguchi, Kin Fai Mak, Jie Shan
Statistical Mechanics · Cross-listed from hep-th
Holographic Dual of PT Symmetric BCFT
Ryota Maeda, Nanami Nakamura and Tadashi Takayanagi
We present a
holographic dual of a two dimensional conformal field theory with non-hermitian but Parity-Time (PT) symmetric boundary conditions, by applying the AdS/BCFT duality and by introducing an imaginary valued scalar field localized on an end-of-the-world brane. We find that as we increase the strength of the non-hermitian PT symmetric interactions, the system experiences a spontaneous PT
symmetry breaking. We also consider its Wick rotated setup as a new
quantum quenched state and show that its growth of
entanglement entropy can be larger than the standard results obtained from standard Cardy states.
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Soft Condensed Matter
Dynamics of monohydroxy alcohols with chain-like structures: Hydrogen bonding lifetime, chain swapping, and Debye process
Shiwang Cheng and Shalin Patil
By assuming reversible H-bonding association and dissociation, this work provides a description of the supramolecular structure and dynamics of monohydroxy alcohols (MAs) within the framework of a recently proposed living chain model (LCM). Structurally, reversible H-bonding leads to a single exponential distribution of the molar concentration of the supramolecular chain with length N. Dynamically, reversible H-bonding enables supramolecular chain breakage and recombination, which modifies the relaxation time of the supramolecular chains. In addition to the structural relaxation, tau_a, and the Debye relaxation, tau_D, two other relaxation times are revealed: the chain breakage time, tau_B, and the H-bonding lifetime, tau_H. The interplay among these four-time scales defines five distinct dynamics regimes. In Regimes I and V, no supramolecular chains form. In Regimes II and IV, supramolecular chains form and give a Debye relaxation. The characteristic chain length scales as Nc~tau_D/tau_a. In these two regimes, the H-bonding lifetime controls the Debye process. In Regime III, large supramolecular chains form. In all regimes with supramolecular chain formation, the Debye relaxation comes from the overall chain end-to-end dipole reorientation and scales with Nc. Excellent agreements between experiments and LCM have been observed, leading to quantitative descriptions of the dielectric and linear viscoelastic properties of MAs. These results thus establish a theoretical framework linking reversible H-bonding interactions to supramolecular structures, dynamics, and macroscopic properties of MAs.
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Strongly Correlated Electrons
Hallmark Signatures of Electronic Pairing in Two-Photon Two-Electron Coincidence Angle-Resolved Photoemission Spectroscopy
Janez Bonca, Alberto Nocera, Andrea Damascelli et al. (+1 more)
Understanding strongly correlated
quantum materials remains a central challenge in condensed matter physics and materials science. While angle-resolved photoemission spectroscopy (ARPES) has become an indispensable probe of single-quasiparticle excitations, it accesses electronic correlations only indirectly. Here we show that unlike one-
photon in, two-electrons out coincidence ARPES ($\gamma\!\rightarrow\!2e$ 2eARPES), the two-
photon in, two-electron out $2\gamma\!\rightarrow\!2e$ 2eARPES provides a direct and unambiguous probe of electronic pairing. We establish this on general theoretical grounds and substantiate it through large-scale numerical simulations of strongly correlated models with both paired and unpaired ground states. The key result is a model-independent separation in the $(\omega_1,\omega_2)$ plane of the two photoelectrons' energies, between signal from electrons emitted from the same pair and signal from electrons emitted from different pairs; this follows from energy conservation alone and is independent of any material-specific assumptions. Our findings demonstrate that $2\gamma\!\rightarrow\!2e$ 2eARPES can identify pairing and extract the pair binding energy as well as the energy of the 'glue'
boson without any sophisticated data analysis or complementary measurements.
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All authors Janez Bonca, Alberto Nocera, Andrea Damascelli, Mona Berciu
Materials Science
Strain induced magnetic phase transition and anomalous transport phenomena in RuO$_2$ and MnF$_2$
Xiuxian Yang, Zhangqi Wu, Xiangju Wang et al. (+6 more)
Collinear antiferromagnets with broken time-reversal
symmetry have emerged as a fertile platform for spintronics. Using a general tight-binding model and first-principles calculations, we show that strain engineering provides a simple route to control
magnetic phase transition and activate transverse responses in representative altermagnets RuO$_2$ and MnF$_2$. For pristine RuO$_2$ and MnF$_2$ with Néel vector $\mathbf{n}\parallel$ [001],
symmetry constrains the off-diagonal elements of the
Hall conductivity tensor to vanish, thereby forbidding anomalous transport and magneto-optical responses. Shear strain applied along the $ac$ direction preserves the
spin symmetry relating the two
spin-opposite
magnetic sublattices and therefore maintains the altermagnetic phase. By contrast, shear strain applied along the $ab$ direction breaks this
spin symmetry and drives a transition from an altermagnetic phase to a partially compensated ferrimagnetic phase in metallic RuO$_2$ and to a fully compensated ferrimagnetic phase in semiconducting MnF$_2$. In addition, the lowered
symmetry enables finite anomalous
Hall, anomalous Nernst, and anomalous thermal
Hall conductivities, as well as magneto-optical rotation angles, which are prohibited in the pristine systems. These responses exhibit a clear strain dependence and become progressively stronger as the strain amplitude increases. Our results establish strain engineering as an effective route to manipulate
magnetic phases and functional responses in unconventional antiferromagnets, thereby expanding opportunities for
antiferromagnetic spintronics and magneto-optical applications.
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All authors Xiuxian Yang, Zhangqi Wu, Xiangju Wang, Shifeng Qian, Ping Yang, Xiaodong Zhou, Jian Hao, Wanxiang Feng, Yinwei Li
Superconductivity
Time-resolved synchronization analysis of stacked intrinsic Josephson junctions of a cuprate superconductor with frequency-modulated terahertz radiation spectra
Masashi Miyamoto, Keisuke Mizoguchi, Ryota Kobayashi et al. (+3 more)
Terahertz radiation from $\text{Bi}_2\text{Sr}_2\text{CaCu}_2\text{O}_{8+\delta}$ intrinsic Josephson junctions (IJJs) provides an ideal platform to study the synchronization of a macroscopic
quantum system. Here, we present a spectral analysis of a frequency-modulated Josephson
plasma emitter coupled with patch
antennas. In the unmodulated intensity distribution as a function of radiation frequency $I_{\mathrm{UM}}(\omega)$, we observe a double Gaussian peak structure. Crucially, double-peak spectra obtained at a constant bias voltage imply either a rapid temporal distribution of resonances or their simultaneous excitation, driven by the mutual electromagnetic coupling between the IJJ mesa and the
antennas. At low modulation frequencies $f_m$, the spectra are well reproduced by the products of $I_{\mathrm{UM}}(\omega)$ and frequency combs, yielding a synchronized relaxation time $\tau_s \simeq 0.28\text{ ns}$. Incorporating $\tau_s$ quantitatively reproduces a drastic spectral transformation observed around $f_m \sim 1\text{ GHz}$, unveiling the sub-nanosecond non-
equilibrium dynamics of coupled Josephson
plasma.
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All authors Masashi Miyamoto, Keisuke Mizoguchi, Ryota Kobayashi, Nozomi Yagyu, Manabu Tsujimoto, Itsuhiro Kakeya