Materials Science · Cross-listed from physics.chem-ph
Real-Time Coupled Electron-Nuclear Dynamics of Chemical Bond Formation: Hydrogen Scattering from a Semiconductor Surface
Jialong Shi, Lingjun Zhu, Florian Nitz et al. (+4 more)
A first-principles coupled electron-
nuclear dynamics simulation based on real-time, time-dependent density functional theory and Ehrenfest dynamics quantitatively repro-duces bimodal translational energy loss and angular distributions observed in experiment for hydrogen atom scattering from Ge(111)-c(2*8). The theory elucidates a site-selective mechanism of electronically nonadiabatic energy transfer associated with the formation of different Ge-H bonds. When a hydrogen atom approaches a Ge rest-atom, it is strongly accelerated toward the potential minimum forming a transient Ge-H bond and then re-flected by the repulsive wall. This transient bond formation triggers an ultrafast electron transfer event from the rest-atom to an adjacent Ge-adatom, involving several crossings between valence and conduction bands of the substrate. Electronic equilibration is impos-sible within such a short time (Born-Oppenheimer failure) allowing the H-atom kinetic energy to be converted to inter-band electronic excitation of the substrate. H-atom colli-sions at other Ge atoms also form a transient bond but exhibit no electronic excitation, resulting in distinctly less efficient energy loss in scattered H-atoms. The nucle-ar-to-electronic energy transfer observed in this system reflects the electronic dynamics of covalent bond formation at a
semiconductor surface, a mechanism that is quite distinct from previously identified nonadiabatic energy transfer mechanisms at metal surfaces mediated by electronic friction or transient negative ions.
Read the full abstract ▾
All authors Jialong Shi, Lingjun Zhu, Florian Nitz, Oliver Bünermann, Alec M. Wodtke, Hua Guo, Bin Jiang
Materials Science · Cross-listed from cs.LG
Universally Converging Representations of Matter Across Scientific Foundation Models
Sathya Edamadaka, Soojung Yang, Ju Li et al. (+1 more)
Machine learning models of vastly different modalities and architectures are being trained to predict the behavior of molecules, materials, and
proteins. However, it remains unclear whether they learn similar internal representations of matter. Understanding their latent structure is essential for building scientific foundation models that generalize reliably beyond their training domains. Although representational convergence has been observed in
language and
vision, its counterpart in the sciences has not been systematically explored. Here, we show that representations learned by nearly sixty scientific models, spanning string-, graph-, 3D atomistic, and
protein-based modalities, are highly aligned across a wide range of chemical systems. Models trained on different
datasets have highly similar representations of small molecules, and machine learning interatomic potentials converge in representation space as they improve in performance, suggesting that foundation models learn a common underlying representation of physical reality. We then show two distinct regimes of scientific models: on inputs similar to those seen during training, high-performing models align closely and weak models diverge into local sub-optima in representation space; on vastly different structures from those seen during training, nearly all models collapse onto a low-information representation, indicating that today's models remain limited by training data and inductive bias and do not yet encode truly universal structure. Our findings establish representational
alignment as a quantitative
benchmark for foundation-level generality in scientific models. More broadly, our work can track the emergence of universal representations of matter as models scale, and for selecting and distilling models whose learned representations transfer best across modalities, domains of matter, and scientific tasks.
Read the full abstract ▾
All authors Sathya Edamadaka, Soojung Yang, Ju Li, Rafael Gómez-Bombarelli
Other Condensed Matter · Cross-listed from quant-ph
Widefield Quantum Sensor for Vector Magnetic Field Imaging of Micromagnetic Structures
Orlando D. Cunha, Filipe Camarneiro, João P. Silva et al. (+4 more)
Many spintronic,
magnetic-
memory, and neuromorphic devices rely on spatially varying
magnetic fields. Quantitatively imaging these fields with full vector information over extended areas remains a major challenge. Existing probes either offer nanoscale resolution at the cost of slow scanning, or widefield imaging with limited vector sensitivity or material constraints.
Quantum sensing with nitrogen-vacancy (NV) centers in diamond promises to bridge this gap, but a practical camera-based vector magnetometry implementation on relevant microstructures has not been demonstrated. Here we adapt a commercial widefield microscope to implement a camera-compatible pulsed optically detected
magnetic resonance protocol to reconstruct stray-field vectors from microscale devices. By resolving the Zeeman shifts of the four NV orientations, we reconstruct the stray-field vector generated by microfabricated permalloy structures that host multiple stable remanent states. Our implementation achieves a spatial resolution of $\approx 0.52 ~\mu\mathrm{m}$ across an $83~\mu\mathrm{m} \times 83~\mu\mathrm{m}$ field of view and a peak sensitivity of $ (828 \pm 142)~\mathrm{nT\,Hz^{-1}}$, with acquisition times of only a few minutes. These results establish pulsed widefield NV magnetometry on standard microscopes as a practical and scalable tool for routine vector-resolved imaging of complex
magnetic devices.
Read the full abstract ▾
All authors Orlando D. Cunha, Filipe Camarneiro, João P. Silva, Hariharan Nhalil, Ariel Zaig, Lior Klein, Jana B. Nieder
Superconductivity
Magnetotransport and Carrier Dynamics in Quasi-One-Dimensional Antiferromagnet KMn$_6$Bi$_5$
Qi-Yuan Liu, Chenfei Shi, Zhaodi Lin et al. (+6 more)
Quasi-one-dimensional materials $A$Mn$_6$Bi$_5$ ($A$ = Na, K, Rb, Cs) exhibit unique electronic behaviors such as antiferromagnetism, charge density waves, and pressure-induced superconductivity. Thus, they serve as a suitable model system to investigate emergent
quantum phenomena produced by the interactions among
spin, charge, and
lattice. Here we report the magnetotransport properties of KMn$_6$Bi$_5$, revealing a cascade of temperature-dependent carrier dynamics. Below 5 K, the system, despite its anisotropic electronic structure, could be effectively described by an isotropic two-band model and exhibits a large, non-saturating magnetoresistance ($\propto B^{1.8}$). Upon warming, a crossover to a single-band regime occurs around 20 K, driven by the suppression of a hole pocket. Electron density recovers as
antiferromagnetic gap openings gradually close from 25 to 70 K which is just below the N$\mathrm{\acute{e}}$el temperature. Within this temperature range, field-quenched
spin fluctuations suppress magnetoresistance. Furthermore, we attribute the low-temperature resistivity upturn to the scaling behavior of magnetoresistance. These findings provide crucial insights into the interplay of dimensionality, magnetism, and electron correlations in quasi-one-dimensional
magnetic semimetals.
Read the full abstract ▾
All authors Qi-Yuan Liu, Chenfei Shi, Zhaodi Lin, Xiutong Deng, Baojuan Kang, Youguo Shi, Gang Wang, Rongrong Jia, Jin-Ke Bao
Materials Science
Revealing Nanoscale Molecular Organization in Liquid Crystals via Cryogenic Atom Probe Tomography
Kuan Meng, Kang'an Wang, Sebastian Eich et al. (+5 more)
While
liquid crystals (LCs) have been extensively studied, obtaining a comprehensive nanoscale picture of their molecular organization remains challenging, as conventional techniques face an intrinsic trade-off between spatial and chemical resolution. Here, cryogenic atom probe
tomography (cryo-APT) is introduced as a new analytical approach for LC materials, using 4'-Pentyl-4-cyanobiphenyl (5CB) and 4'-Octyl-4-cyanobiphenyl (8CB) as representative model compounds. This was enabled by a tailored cryogenic focused ion beam (cryo-FIB) protocol optimized for small organic molecules. The method enables controlled field evaporation of both intact molecules and diagnostic fragments, achieving over 90% molecular retention while preserving four characteristic dissociation patterns. By spatially correlating these fragmentation profiles with the local electric field derived from the tip geometry, we reveal field-directed dissociation pathways of CB molecules. In parallel, the distribution of intact molecular ions enables nanoscale visualization of material structure: we resolve homogeneous mixing of 5CB and 8CB in the nematic phase and directly observe the sub-nanometer crystalline layering in a supercooled 8CB sample, with contrast to the surrounding amorphous
matrix suggesting the presence of a solid-
liquid interface. This work establishes cryo-APT as a new powerful analytical platform for LC research and reveals its broad potential for application in soft matter systems.
Read the full abstract ▾
All authors Kuan Meng, Kang'an Wang, Sebastian Eich, Pierre Nacke, Johanna R. Bruckner, Patrick Stender, Frank Giesselmann, Guido Schmitz
Superconductivity
Revisiting Phase Stability and Superconductivity in Ca-H Superhydrides with Anharmonic Effects
Wenbo Zhao, Zefang Wang, Ying Sun et al. (+3 more)
The prediction of superconductivity above 200 K in CaH$_6$ revolutionized research on hydrogen-rich
superconductors, and subsequent experiments have verified this prediction, while unidentified peaks in XRD and the decrease in superconducting temperature upon decompression indicate that unresolved issues remain. In this work, we reconstructed the accurate temperature-pressure phase diagram of the Ca-H system and determined the stability ranges of its candidate superconducting phases by considering anharmonic effects. Our results demonstrate that type-I clathrate Ca$_8$H$_{46-delta}$ structures become thermodynamically stable at 0 K when anharmonic effects are considered. Notably, we found that the previously predicted CaH$_6$ phase achieves stability above 500 K, underscoring the significant role of temperature and anharmonic effects in stabilizing this intriguing high-pressure phase. Our findings offer insights into the structure and superconducting mechanisms of hydrides.
Read the full abstract ▾
All authors Wenbo Zhao, Zefang Wang, Ying Sun, Hefei Li, Hanyu Liu, Yu Xie
Mesoscale and Nanoscale Physics
Spin-flop driven interfacial tunneling magnetoresistance in an antiferromagnetic tunnel junction
Xiaolin Ren, Ruizi Liu, Yiyang Zhang et al. (+6 more)
The utilization of two-dimensional (2D) materials in
magnetic tunnel junctions (MTJs) has shown excellent performance and rich physics. As for 2D antiferromagnets, the
magnetic moments in different layers respond asynchronously and can be configured at various states under different
magnetic fields, showing the possibility of efficient
magnetic and electrical tunability. In this report, A-type
antiferromagnetic (AFM) material (Fe0.5Co0.5)5GeTe2 (FCGT) works as electrodes to realize full van der Waals
magnetic tunnel junctions. Owing to the interfacial effect, the even-layer FCGT, although with zero net magnetization, exhibits
spin selectivity in MTJ architecture contributing to a tunneling magnetoresistance (TMR) reaching about 25% at a low operating current 1 nA at 100 K and persists near room temperature. Due to the surface
spin-flop (SSF) effect in
antiferromagnetic FCGT, the alternation flexibility between the volatile and nonvolatile
memory behavior is achieved. The interfacial TMR can be tuned efficiently in amplitude and even sign under different bias currents and temperatures. These findings show precise magnetoelectric manipulation in MTJs based on 2D antiferromagnets and highlight the promise of 2D antiferromagnets for spintronic devices.
Read the full abstract ▾
All authors Xiaolin Ren, Ruizi Liu, Yiyang Zhang, Yuting Liu, Xuezhao Wu, Kun Qian, Kenji Watanabe, Takashi Taniguchi, Qiming Shao
Materials Science
DEM Simulations of Spheres Flowing Through a Hopper: Validation of Beverloo Law
Leticia M. V. da Silva, Erlifas Moreira Rocha, Piter Gargarella et al. (+1 more)
This work presents a detailed investigation of the discharge behavior of spherical granular materials through a conical–cylindrical hopper using Discrete Element Method (DEM) simulations. The aim is to assess the applicability limits of the empirical Beverloo law. The system was modeled with a monodisperse particles whose mechanical properties correspond to the $Al_{95}Fe_2Cr_2Ti_1$
alloy, and interparticle contacts were described using the Hertz–Mindlin (no slip) model. The simulations systematically explored the influence of particle diameter ($d$) and bed height ($h$) on the resulting mass flow rate ($Q$). The results reveal the coexistence of transient and steady-state discharge regimes. Good agreement with the Beverloo scaling was observed for relatively small diameter ratios ($D/d = 10$) and sufficiently large bed heights, where the flow stabilizes rapidly. For larger $D/d$ ratios, the discharge rate decays exponentially, indicating a breakdown of the constant-hydrostatic-pressure assumption underlying the Beverloo model. A dimensionless criterion for the validity of the Beverloo law is proposed as $\Pi_h = h/D > 2$, or equivalently $N = h/d > 20$. The quantitative agreement between DEM simulations and experimental measurements for polydisperse particle size distributions further validates the computational model and demonstrates its predictive capability for granular discharge in confined geometries.
Read the full abstract ▾
All authors Leticia M. V. da Silva, Erlifas Moreira Rocha, Piter Gargarella, Pedro Augusto F. P. Moreira
Materials Science
Terahertz light driven coherent excitation of a zone-folded Raman-active phonon mode in the Spin-Ladder System $\alpha'$-NaV$_2$O$_5$
Flavio Giorgianni, Martina Romani, Pascal Puphal et al. (+5 more)
We investigate the out-of-
equilibrium lattice dynamics in the
spin-ladder system $\alpha'$-NaV$_2$O$_5$ using intense terahertz (THz) pump and near-infrared (NIR) probe spectroscopy. When quasi-single-cycle THz pulses interact with $\alpha'$-NaV$_2$O$_5$ in its low-temperature, dimerized charge-ordered phase, they induce coherent oscillations in the time domain at the zone-folded Raman-active
phonon frequency of 1.85 THz. By combining pump-probe measurements with
lattice dynamics modeling based on equation-of-motion approach, we propose that these oscillations arise from a nonlinear coupling between Raman-active and infrared (IR)-active
phonon modes, with the latter being resonantly excited by the THz pulses. In contrast, excitation with NIR femtosecond
laser pulses does not produce measurable vibrational dynamics, highlighting the unique potential of THz-driven, nonlinear light-matter interactions for the coherent and selective control of structural dynamics in
quantum materials.
Read the full abstract ▾
All authors Flavio Giorgianni, Martina Romani, Pascal Puphal, Masahiko Isobe, Leonie Spitz, Mariangela Cestelli Guidi, Carlo Vicario, Mattia Udina
Strongly Correlated Electrons
More is uncorrelated: Tuning the local correlations of SU($N$) Fermi-Hubbard systems via controlled symmetry breaking
Edoardo Zavatti, Gabriele Bellomia, Matteo Ferraretto et al. (+2 more)
Cold-atom experiments based on alkali-like atoms provide us with a tool to experimentally realize Hubbard models with a large number $N$ of components. The value of $N$ can be seen as a new handle to tune the properties of the system, leading to new physics both in the case of fully SU($N$) symmetric systems, or in the presence of controlled
symmetry breaking. We focus on the Mott transition at global half filling and we characterize local correlations between particles through the inter-
flavor mutual information, an experimentally accessible quantity that rigorously measures the distance from the closest gaussian state, unveiling features that cannot be accessed by conventional probes of Mottness. We prove that these correlations are fully independent from local
entanglement and
quantum discord, and, using Dynamical Mean-Field Theory, we show that the SU(4) system has significantly smaller correlations than the SU(2) counterpart. In the atomic limit we prove that increasing $N$ further decreases the strength of the correlations. This suggests that a controlled reduction of the
symmetry, reducing the number of effective components, can be used to enhance the degree of correlation. We confirm this scenario solving the model for $N=4$ and gradually breaking the
symmetry via a Raman field, revealing an
evolution from the SU(4) to the SU(2) Mott transition as the
symmetry-breaking term increases, with a sudden recovery of the large correlations of the SU(2) model at weak Raman coupling in the Mott state. By further exploring the interplay between energy repulsion and the Raman field, we obtain a rich phase diagram with three different phases – a metal, a band
insulator, and a Mott
insulator – all coexisting at a single tricritical point.
Read the full abstract ▾
All authors Edoardo Zavatti, Gabriele Bellomia, Matteo Ferraretto, Samuele Giuli, Massimo Capone
Superconductivity
Double-Bridge Mechanism for Enhancing Tc in Oxide Superconductors
Jun-jie Shi, Juan Du and Yao-hui Zhu
We propose a new double-bridge mechanism to significantly enhance $T_c$ in ionic
oxide superconductors. Based on our recently proposed ionic-bond-driven O/Cu-bridged (bridge-I) pairing e$^-$-O-e$^-$/h$^+$-Cu-h$^+$ formed in the pseudogap phase ($T_c<T<T^*$), we reveal a key bridge-II Cu/O-mediated inter-pair attraction that overcomes direct Coulomb repulsion and drives coherent Bose-Einstein condensation (BEC) of preformed Cooper pairs. Within the BEC framework (Eq.(3)), $T_c$ follows the Uemura scaling $(n_{\rm pair}^{\rm 3D})^{2/3}/m_{\rm pair}^*$ or $n_{\rm pair}^{\rm 2D}/m_{\rm pair}^*$ and increases linearly with the attractive scattering length $a<0$. Strengthening bridge-II attraction, minimizing $m_{\rm pair}^*$, and optimizing $n_{\rm pair}^{\rm 3D}$ are the key to maximizing $T_c$. This double-bridge mechanism unifies the eV-scale strong pairing at room temperature and BEC, provides a universal route toward higher $T_c$, and guides the design of next-generation
superconductors.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Nonrelativistic Functional Properties in Collinear Antiferromagnets Based on Multipole Representation Theory
Yuuki Ogawa and Satoru Hayami
In recent years, the concept of multipoles has been widely used to describe and classify various
magnetic and electric responses in solids, providing a systematic way to identify
symmetry-allowed or -forbidden physical responses. Conventionally, multipole classifications rely on the
magnetic point group of a system, which inherently incorporates the effects of relativistic
spin-orbit coupling because the
spin orientation is supposed to follow the point-group transformation of the
lattice. However, this approach becomes insufficient in situations where relativistic
spin-orbit coupling is negligibly weak or where the
spin and orbital (
lattice) degrees of freedom are decoupled, thereby requiring a more comprehensive
symmetry description. In this work, we introduce a multipole description on the basis of the
spin-point-group
symmetries, enabling a systematic exploration of nonrelativistic phenomena that persist even without
spin-orbit coupling in a collinear antiferromagnet. As an application, we theoretically demonstrate
spin-current generation driven by elastic waves in a specific collinear antiferromagnet, fully independent of
spin-orbit coupling.
Read the full abstract ▾
Materials Science
Tuning spin currents in collinear antiferromagnets and altermagnets
Sajjan Sheoran and Pratibha Dev
Spin current generation through non-relativistic
spin splittings, found in uncompensated magnets and d-wave altermagnets, is desirable for low-power spintronics. Such
spin currents, however, are
symmetry forbidden in conventional collinear antiferromagnets and higher-order altermagnets. Using
spin point group analysis, we demonstrate that finite
spin currents can be induced in these materials via magnetoelectric, piezomagnetic, and piezomagnetoelectric-like couplings. We utilize electric fields, strain, and their combinations to drive
symmetry-lowering phase transitions into uncompensated
magnetic or d-wave altermagnetic states, thereby enabling finite
spin conductivity in a broader class of
magnetic materials. We further substantiate this framework using density functional theory and Boltzmann transport calculations on representative
magnetic materials - KV2Se2O, RuF4 , Cr2O3 , FeS2 , and MnPSe3 - spanning these different cases. The charge-to-
spin conversion ratio reaches up to almost 100% via uncompensated magnetism and about 40% via d-wave altermagnetism under realistic conditions, highlighting the effectiveness of this approach for efficient
spin current generation.
Read the full abstract ▾
Materials Science
DHICA ion-modified melanin based porous Si solar cell
M. Semenenko, T. Yu. Obukhova, S. O. Kravchenko et al. (+8 more)
This work studies photosensitivity and current-voltage characteristics under illumination of water-soluble eumelanin films based on DHICA tetramers and hybrid eumelanin/porous Si photovoltaic
cells aimed at optimizing their characteristics. By using DMSO to dissolve melanin containing protonated carboxyl groups and to remove ammonium cations, it became possible to significantly reduce the ionic component of conductivity, thus improved the electron transport. It was found out that dissolution in DMSO provides a denser {\pi}-{\pi} stacking of DHICA tetramers, which led to a significant improvement in the photovoltaic
cell parameters. In particular, the efficiency increased from 0.023 % to 4.4 % and the series resistance decreased from 119 {\Omega} to 42.6 {\Omega}. Modeling demonstrated that high-temperature annealing, which causes decarboxylation, leads to a structural rearrangement of tetramers from a Christmas tree-like configuration to a "toothed helix". At this, one of the planes partially straightens. This emphasizes the critical importance of the morphology of the organic layer for photogeneration of carriers in a heterojunction.
Read the full abstract ▾
All authors M. Semenenko, T. Yu. Obukhova, S. O. Kravchenko, O. S. Pylypchuk, O. Yu. Ostapenko, T. O. Kuzmenko, M. V. Voitovych, S. Davidenko, Ye. S. Davidenko, S. S. Davidenko, A. Sarikov
Quantum Gases
Optimizing two-qubit gates for ultracold fermions in optical lattices
Jan A. P. Reuter, Juhi Singh, Tommaso Calarco et al. (+2 more)
Ultracold neutral atoms in optical
lattices are a promising platform for simulating the behavior of complex materials and implementing
quantum gates. We optimize collision gates for fermionic Lithium atoms confined in a double-well potential, controlling the
laser amplitude and keeping its relative phase constant. We obtain high-fidelity gates based on a one-dimensional confinement simulation. Our approach extends beyond earlier
Fermi-Hubbard simulations by capturing a momentum dependence in the interaction energy. This leads to a higher interaction strength when atoms begin in separate subwells compared to the same subwell. This momentum dependence might limit the gate fidelity under realistic experimental conditions, but also enables tailored applications in
quantum chemistry and
quantum simulation by optimizing gates for each of these cases separately.
Read the full abstract ▾
All authors Jan A. P. Reuter, Juhi Singh, Tommaso Calarco, Felix Motzoi, Robert Zeier
Materials Science
Evaluation of Foundational Machine Learned Interatomic Potentials for Migration Barrier Predictions
Achinthya Krishna Bheemaguli, Penghao Xiao and Gopalakrishnan Sai Gautam
Fast, and accurate prediction of ionic migration barriers ($E_m$) is crucial for designing next-generation battery materials that combine high energy density with facile ion transport. Given the computational costs associated with estimating $E_m$ using conventional density functional theory (DFT) based nudged elastic band (NEB) calculations, we
benchmark the accuracy in $E_m$ and geometry predictions of five foundational machine learned interatomic potentials (MLIPs), which can potentially accelerate predictions of ionic transport. Specifically, we assess the accuracy of MACE-MP-0, Orb-v3, SevenNet, CHGNet, and M3GNet models, coupled with the NEB framework, against DFT-NEB-calculated $E_m$ across a diverse set of battery-relevant chemistries and structures. Notably, MACE-MP-0 and Orb-v3 exhibit the lowest mean absolute errors in $E_m$ predictions across the entire
dataset and over data points that are not outliers, respectively. Importantly, Orb-v3 and SevenNet classify `good' versus `bad' ionic conductors with an accuracy of $>$82%, based on a threshold $E_m$ of 500~meV, indicating their utility in high-throughput screening approaches. Notably, intermediate images generated by MACE-MP-0 and SevenNet provide better initial guesses relative to conventional interpolation techniques in $>$71% of structures, offering a practical route to accelerate subsequent DFT-NEB relaxations. Finally, we observe that accurate $E_m$ predictions by MLIPs are not correlated with accurate (local) geometry predictions. Our work establishes the use-cases, accuracies, and limitations of foundational MLIPs in estimating $E_m$ and should serve as a base for accelerating the discovery of novel ionic conductors for batteries and beyond.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
From fractional Chern insulators to topological electronic crystals in moiré MoTe2: quantum geometry tuning via remote layer
Feng Liu, Fan Xu, Cheng Xu et al. (+18 more)
The
quantum geometry of Bloch wavefunctions,encoded in the Berry
curvature and
quantum metric, is believed to be a decisive ingredient in stabilizing fractional
quantum anomalous
Hall (FQAH) effect(i.e., fractional Chern
insulator, FCI, at zero
magnetic field), against competing
symmetry-breaking phases.A direct experimental demonstration of
quantum geometry-driven switching between distinct correlated topological phases, however, has been lacking. Here, we report experimental evidence of such a switch in a high-quality 3.7 twisted MoTe2 (tMoTe2) device consisting of both A-A
bilayer and A-AB trilayer regions. While composite
Fermi liquid CFL/FQAH phases are established in A-A tMoTe2,the A-AB region-effectively an A-A moire
bilayer proximitized by a remote B layer-develops a series of topological electronic
crystal (TEC, also referred to as generalized QAH
crystal, QAHC) states with integer quantized
Hall conductance at commensurate fractional fillings v=1/2, 2/3, and an incommensurate filling factor v=0.53.The electrostatic phase diagram is mapped out by combined transport and optical measurements, showing that these TEC states emerge within the first moir'e valence band prior to any charge transfer to the B layer. Exact diagonalization (ED) incorporating the remote-layer-induced intralayer potential demonstrates a transition from a CFL-like
manifold in the A-A limit to a Chern number C=1 ground-state consistent with a TEC at v=1/2 , accompanied by the further breakdown of ideal band geometry. Our results provide experimental evidence of
quantum geometry-tuned competition between FQAH/CFL and TEC phases in a moiré Chern band and pave the way for further exploring correlation-driven topological phenomena by tuning
quantum geometry.
Read the full abstract ▾
All authors Feng Liu, Fan Xu, Cheng Xu, Jiayi Li, Zheng Sun, Jiayong Xiao, Ning Mao, Xumin Chang, Xinglin Tao, Kenji Watanabe, Takashi Taniguchi, Jinfeng Jia, Ruidan Zhong, Zhiwen Shi, Shiyong Wang, Guorui Chen, Xiaoxue Liu, Dong Qian, Yang Zhang, Tingxin Li, Shengwei Jiang
Strongly Correlated Electrons
Fermionic Critical Fluctuations: Potential Driver of Strange Metallicity and Violation of the Wiedemann-Franz Law in YbRh2Si2
Frank Steglich
Results of combined thermal and electrical transport measurements through the
magnetic field-induced
quantum critical point in the heavy-
fermion compound YbRh2Si2 are revisited to explore the relationship between the strange-metal behavior, observed in both the electrical and electronic thermal resistivity, and the violation of the Wiedemann-Franz law in the zero-temperature limit. A new type of inelastic scattering center for the charge and heat carriers has been detected and ascribed to the small-to-large
Fermi-surface fluctuations. These are operating in the vicinity of and at the Kondo-destroying
quantum critical point as fermionic
quantum critical fluctuations and are considered the primary driver of the strange-metal behavior and the violation of the Wiedemann-Franz law.
Read the full abstract ▾
Soft Condensed Matter
Hamiltonian Active Particles in Incompressible Fluid Membranes
Sneha Krishnan and Rickmoy Samanta
Active
proteins and membrane-bound motors exert force dipole flows along fluid interfaces and lipid
bilayers. We develop a
Hamiltonian framework for the interactions of pusher and puller dipoles embedded in an incompressible two-dimensional membrane supported by a shallow viscous subphase. Beginning from the Brinkman-regularized Stokes equations of the membrane-subphase system, we construct the near-field and far-field dipolar velocity fields and associated stream functions. For two quenched (fixed orientation) dipoles, we obtain exact analytic solutions in both the near- and far-field regimes. Although generic dipoles reorient under local membrane vorticity, we show that the far-field dipolar flow is vorticity-free; force-free motors therefore retain fixed orientations and obey a position-based
Hamiltonian dynamics in which the positions of $N$ dipoles evolve via an effective
Hamiltonian built from the dipolar stream function. In the near field, where the flow possesses finite vorticity, a
Hamiltonian formulation is recovered in the quenched-orientation limit. For identical dipoles, the far-field
Hamiltonian produces rapid clustering from random initial conditions, whereas the near-field
Hamiltonian suppresses collapse leading to non-aggregating configurations. The phase portraits reveal that the many-body collapse observed in the time
evolution of the far field
Hamiltonian arises from angular transport across phase space enabled by the screened hydrodynamic interaction. Our work thus provides a concrete realization of a position-based
Hamiltonian formulation for active particles in incompressible fluid membranes and shows that hydrodynamic screening can reorganize both the dynamical phase space and the collective organization of active dipoles.
Read the full abstract ▾
Materials Science
High Pressure and Compositionally Directed Route to a Hexagonal GeSn Alloy Class
George Serghiou, Hans Josef Reichmann, Gang Ji et al. (+4 more)
Despite their electronic dominance, cubic diamond structured Si and Ge, are optoelectronically deficient. Recent work indicates, however, that a volume-expanded hexagonal Ge modification can exhibit intensely sought, superior optoelectronic characteristics. If larger Sn could form a hexagonal solid solution with Ge, this would achieve this expansion. But this was not expected because Ge and Sn are unreactive at ambient conditions, Sn does not have an ambient hexagonal
symmetry, and only cubic or tetragonal binary modifications could be prepared under any conditions including thin film processing. This state of affairs is categorically changed here by subjecting Ge and Sn to pressures of 9 and 10 GPa and temperatures up to 1500 K using large-volume press methods. Synchrotron angle-dispersive X-ray diffraction, precession electron diffraction and chemical analysis using electron microscopy reveal ambient pressure recovery of hexagonal 2H, 4H and 6H Ge-Sn solid solutions (P63/mmc). Formation of this new binary materials landscape is correlated with Sn uptake, with the hexagonal
symmetry being accessible below 21 atom % Sn and the cubic diamond
symmetry at or above this value. The findings form fertile routes to advanced materials, by in tandem creating reactivity with pressure and directing production of needed
crystal symmetries with composition, as well as opportunity to tune properties based on
crystal symmetry, composition, and stacking sequence for optoelectronic applications. PubMed Disclaimer
Read the full abstract ▾
All authors George Serghiou, Hans Josef Reichmann, Gang Ji, Laurence Nigay, Jonathan P. Wright, Daniel J. Frost, Gus Calder
Mesoscale and Nanoscale Physics
Numerical simulation of coherent spin-shuttling in a QuBus with charged defects
Nils Ciroth, Arnau Sala, Ran Xue et al. (+4 more)
Recent advances in coherent conveyor-mode
spin qubit shuttling are paving the way for large-scale
quantum computing platforms with
qubit connectivity achieved by
spin qubit shuttles. We developed a simulation tool to investigate numerically the impact of device imperfections on the
spin-coherence of conveyor-mode shuttling in Si/SiGe. We simulate the
quantum evolution of a mobile electron
spin-
qubit under the influence of sparse and singly charged point defects placed in the Si/SiGe
heterostructure in close proximity to the shuttle lane. We consider different locations of a single charge defect with respect to the center of the shuttle lane, multiple orbital states of the electron in the shuttle with $g$-factor differences between the orbital levels, and orbital relaxation induced by electron-
phonon interaction. With this simulation framework, we identify the critical defect density of charged point defects in the
heterostructure for conveyor-mode
spin qubit shuttle devices and quantify the impact of a single defect on the coherence of a
qubit.
Read the full abstract ▾
All authors Nils Ciroth, Arnau Sala, Ran Xue, Lasse Ermoneit, Thomas Koprucki, Markus Kantner, Lars R. Schreiber
Materials Science
Static and dynamic properties of the frustrated spin-1/2 depleted-kagome antiferromagnet Cu$_7$(TeO$_3$)$_2$(SO$_4$)$_2$(OH)$_6$
K. U. Akshay, Sebin J. Sebastian, Q.-P. Ding et al. (+2 more)
The structural and
magnetic properties of the two-dimensional
spin-$1/2$ depleted-kagome compound Cu$_7$(TeO$_3$)$_2$(SO$_4$)$_2$(OH)$_6$ are investigated using x-ray diffraction, magnetization, heat capacity, and $^1$H
Nuclear Magnetic Resonance (NMR) measurements. From the analysis of
magnetic susceptibility, we found a large Curie-Weiss temperature [$\theta_{\rm CW} = -50(2)$ K] and the co-existence of
antiferromagnetic and
ferromagnetic interactions. The value of $\theta_{\rm CW}$ gives an estimate of the average nearest-neighbour
antiferromagnetic interaction of $J/k_{\rm B} \simeq 66$ K. The NMR relaxation rates ($1/T_1$ and $1/T_2$) exhibit a peak, providing evidence for a
magnetic long-range order at $T^*\simeq 4$ K which appears to be canted
antiferromagnetic type. Heat capacity also features a broad maximum at $T^*$ that moves towards higher temperatures with increasing
magnetic field, reflecting defect induced Schottky anomaly. The frustration parameter $f_r = \lvert \theta_{\rm CW} \lvert/{T^{*}}\simeq 12.5$ renders the compound a highly frustrated low-dimensional magnet.
Read the full abstract ▾
All authors K. U. Akshay, Sebin J. Sebastian, Q.-P. Ding, Y. Furukawa, R. Nath
Statistical Mechanics · Cross-listed from quant-ph
Edge bits in average symmetry protected topological mixed state
Yoshihito Kuno
Edge bit in an average
symmetry protected topological (ASPT) mixed state is studied. The state is protected by one strong $Z_2$ and one weak (average) $Z_2$
symmetries. As analogous objects of pure
symmetry protected topological (SPT) states, the ASPT possesses edge bits. In particular, the analogous operator response exists, that is,
symmetry fractionalization. The fractionalization preserves the presence of the ASPT in the bulk, and the fractionalized edge operators acting on the edge bits of the ASPT. %analogous to the ones in the pure SPTs. In this work, based on the cluster model and by employing Choi mapping, we discuss generic features of the edge bits and numerically clarify the behavior of the edge bits and their robustness for varying decoherence and perturbative interactions. By using an operator-space mutual information (OSMI), we track the flow of
quantum correlations between the two edges. Remarkably, even in the ASPT regime, a finite portion of the initial edge-to-edge correlation survives.
Read the full abstract ▾
Disordered Systems and Neural Networks
Stretched Exponential Scaling of Parity-Restricted Energy Gaps in a Random Transverse-Field Ising Model
G.-X. Tang, J.-Z. Zhuang, L.-M. Duan et al. (+1 more)
The success of a
quantum annealing
algorithm requires a
polynomial scaling of the energy gap. Recently it was shown that a two-dimensional transverse-field Ising model on a square
lattice with nearest-neighbor $\pm J$ random coupling has a
polynomial energy gap in the symmetric subspace of the parity operator [Nature 631, 749-754 (2024)], indicating the efficient preparation of its ground states by
quantum annealing. However, it is not clear if this result can be generalized to other
spin glass models with continuous or biased randomness. Here we prove that under general independent and identical distributions (i.i.d.) of the exchange energies, the energy gap of a one-dimensional random transverse-field Ising model follows a stretched exponential scaling even in the parity-restricted subspace. We discuss the implication of this result to
quantum annealing problems.
Read the full abstract ▾
All authors G.-X. Tang, J.-Z. Zhuang, L.-M. Duan, Y.-K. Wu
Materials Science
High Thermoelectric Performance via Stacking-Controlled Symmetry Breaking in Layered XZnBi (X = Rb, Cs) Zintl Materials
Aadil Fayaz Wani, Nirma Kumari, SuDong Park et al. (+1 more)
High thermoelectric efficiency requires high Seebeck coefficient, high electrical conductivity, and low thermal conductivity. However, strategies that suppress thermal conductivity often simultaneously degrade electrical conductivity, making effective electrical-thermal decoupling highly challenging. Here, we show that atomic-layer stacking order change in XZnBi (X = Rb, Cs) provides an efficient route to achieve such decoupling. Even though electronic transport coefficients and relaxation times remain largely insensitive to stacking order due to preserved
Fermi-surface
topology, the
lattice thermal conductivity exhibits a strong stacking dependence, with AB stacking significantly suppressing it below 1 Wm$^{-1}$K$^{-1}$ at temperatures above 300 K. The stacking transition from AA to AB breaks structural
symmetries. It increases the three-
phonon phase space and available scattering channel, substantially suppressing
phonon transport by about 50$\%$ in both materials. As a result, the AB-stacked phases yield high ZT values of 1.96 (1.69) in n-type CsZnBi (RbZnBi) at 900 K, which is about 40$\%$ (30$\%$) higher than AA stacking. These findings establish the XZnBi family as promising thermoelectric candidates and highlight stacking-order controlled
phonon transport as a robust strategy for advancing thermoelectric material design.
Read the full abstract ▾
All authors Aadil Fayaz Wani, Nirma Kumari, SuDong Park, Byungki Ryu
Mesoscale and Nanoscale Physics
Current switching behavior mediated via hinge modes in higher-order topological phases using altermagnets
Minakshi Subhadarshini, Amartya Pal and Arijit Saha
We propose a theoretical framework to engineer hybrid-order and higher-order topological phases in three-dimensional topological
insulators by coupling to $d$-wave altermagnets (AMs). Presence of only $d_{x^2-y^2}$-type AM drives the system into a hybrid-order topological phase where both first-order and second-order topological phases coexist. This phase is characterized by spectral analysis, low-energy surface theory, dipolar and quadrupolar winding numbers, and it's signature is further confirmed by two-terminal differential conductance calculations. Incorporation of the $d_{x^2-z^2}$-type AM drives the system into two second-order topological
insulator phases hosting distinct type of hinge modes. These two variants of second-order topological phases are also topologically characterized by spectral analysis, topological invariants, low-energy surface thoery, and transport calculations. Importantly, the localization and direction of propagation of these one-dimensional hinge modes are controllable by tuning the relative strengths of the alermagnetic exchange orders. We utilize this feature to propose a tunable current-switching behaviour mediated via the hinge modes. Our results establish AMs based hybrid structure as a versatile platform for controllable higher-order
topology and hinge-mediated device applications.
Read the full abstract ▾
Soft Condensed Matter
Invariant fractocohesive length in thermally aged elastomers
Aimane Najmeddine, Santiago Marin, Zhen Xu et al. (+3 more)
The fractocohesive length - the ratio between fracture toughness and work-to-fracture - provides a material-specific length scale that characterizes the size-dependent fracture behavior of pristine elastomers. However, its relevance to thermally aged materials, where both toughness and work of fracture degrade dramatically, remains unexplored. Here, we demonstrate that despite severe thermal embrittlement, the fractocohesive length remains invariant throughout thermal aging, independent of temperature or duration. We verify this invariance experimentally for two elastomer systems (Styrene Butadiene Rubber and Silicone Rubber) at multiple aging temperatures for aging times up to eight weeks. This finding bridges a critical gap in fracture mechanics of aged
polymers: while the
evolution of work-to-fracture can be predicted from well-established constitutive models that track network changes (crosslink density and chain scission), the
evolution of fracture toughness has lacked predictive frameworks. The invariance of fractocohesive length enables direct calculation of fracture toughness at any aging state from the predicted work of fracture, eliminating the need for extensive fracture testing on aged elastomers and providing a crucial missing link for computational fracture predictions in aged elastomeric components.
Read the full abstract ▾
All authors Aimane Najmeddine, Santiago Marin, Zhen Xu, Connor Thompson, Guoliang Liu, Maryam Shakiba
Materials Science
Unconventional Magneto-Optical Effects in Altermagnets
Yongpan Li, Yichen Liu and Cheng-Cheng Liu
The ideal altermagnets are a class of collinear,
crystal-
symmetry-enforced fully compensated magnets with nonrelativistic
spin-split bands, in which contributions from Berry
curvature to magneto-optical effects (MOEs) are strictly forbidden by an effective time-reversal
symmetry. Here we show that, in such systems, MOEs are exclusively induced by the
quantum metric and, in realistic altermagnets, are typically dominated by it. We refer to Berry-
curvature-induced MOEs as conventional MOEs and to
quantum-metric-dominated MOEs as unconventional MOEs. We derive general formulas that incorporate both Berry
curvature and
quantum metric for unconventional MOEs in altermagnets, enabling a quantitative evaluation of their respective contributions. Through
symmetry analysis, we prove that ideal altermagnets are constrained to exhibit only unconventional MOEs. Using the three-dimensional canonical altermagnet MnTe and the emerging two-dimensional
bilayer twisted altermagnet CrSBr as illustrative examples, we demonstrate that unconventional MOEs are prevalent in altermagnets. Our results establish altermagnets as a natural platform for
quantum-metric-driven optical phenomena, substantially broadening the scope of MOEs and providing concrete predictions that can be tested in future experimental studies.
Read the full abstract ▾
Materials Science · Cross-listed from physics.chem-ph
Zero-Waste Biorefinery: Pyrolysis of Fermentation Residues into Catalytic Biochar for Circular Biohydrogen Systems
Muhammad Shahzaib
This study presents a closed-loop biorefinery strategy that thermochemically upcycles fermentation residues (FRs) from photo-fermentative biohydrogen production (PFHP) into functional biochar catalysts, thereby enhancing the efficiency of the initial PFHP process. Four FRs derived from hydrothermal and ethylene glycol-pretreated corn stover were pyrolyzed at 700{\deg}C. Multi-model kinetic analyses revealed
diffusion-controlled mechanisms with activation energies ranging from 157 to 278 kJ/mol, while thermodynamic profiling highlighted the influence of feedstock composition on reaction spontaneity and
entropy. Pyrolysis effectively restored porosity compromised during fermentation, yielding biochar with tailored properties: microporous BC3 (185 m2/g) from oxygen-rich precursors and mesoporous BC4 (76.58 m2/g) from graphitized residues. When reintroduced into PFHP, BC3 maximized cumulative hydrogen yield (570 mL) via pH buffering, and BC4 achieved the highest production rate (14.91 mL/h) through electron shuttle mechanisms. The integrated process concurrently generated syngas, bio-oil, and catalytic biochar, enabling waste valorization, renewable energy output, and process enhancement within a circular bioeconomy framework.
Read the full abstract ▾
Soft Condensed Matter
Critical fluctuations of elastic moduli in jammed solids
Kumpei Shiraishi and Hideyuki Mizuno
We investigate sample-to-sample fluctuations of the shear modulus in ensembles of particle packings near the jamming transition. Unlike the average modulus, which exhibits distinct scaling behaviours depending on the interparticle potential, the fluctuations obey a critical exponent that is independent of the potential. Furthermore, this scaling behaviour has been confirmed in two-dimensional packings, indicating that it holds regardless of spatial dimension. Using this scaling law, we discuss the relationship predicted by heterogeneous-elasticity theory between elastic-modulus fluctuations and the Rayleigh scattering of sound waves across different pressures. Our numerical results provide a useful foundation for developing a unified theoretical description of the jamming critical phenomenon.
Read the full abstract ▾