Materials Science · Cross-listed from physics.bio-ph
Structural gradients and strain partitioning across the mouse Achilles tendon enthesis revealed by in situ X-ray scattering
Isabella Silva Barreto, Moritz L. Stammer, Moritz P.K. Frewein et al. (+8 more)
The enthesis is the insertion site of tendon into bone and exhibits a high mechanical durability despite the large mismatch in material properties between the two tissues. This durability stems from gradients in composition, structure and organization on multiple hierarchical length scales. Despite extensive research on enthesis structure and mechanics, the local deformation mechanisms are poorly understood. Synchrotron scanning small- and wide-angle X-ray scattering was combined with in situ tensile testing of the mouse Achilles tendon enthesis to extensively map the mechanical response of the collagen fibrils and molecules as well as the hydroxyapatite mineral particles and
crystals. Gradients in nano- and molecular scale structure and a stronger and more immediate deformation response towards the interface compared to further away were observed in both the soft and mineralized tissue. The strain decreased progressively across hierarchical levels; with an applied tissue strain of 20% the nanoscale fibrils were strained by ~1-2%, the collagen molecules by ~0.5% and the hydroxyapatite
crystals by ~0.05%, thus following an approximate ratio of 1 : 0.1 : 0.01 : 0.001. These results show that load transfer across the enthesis is both spatially heterogeneous and hierarchy-dependent. This indicates that the graded attachment accommodates deformation through region-specific load sharing and hierarchical strain partitioning, consistent with a contribution from dissipation within the non-collagenous
matrix. In doing so, the enthesis can mitigate stress concentrations and maintain mechanical integrity across the tendon-to-bone transition.
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All authors Isabella Silva Barreto, Moritz L. Stammer, Moritz P.K. Frewein, Claire Camy, Juraj Todt, Michael Meindlhumer, Jozef Keckes, Stefano Checchia, Sandrine Roffino, Martine Pithioux, Tilman A. Grünewald
Quantum Gases · Cross-listed from quant-ph
Efficient ensemble randomization by tuning chaos in a nonlinear spin-1 system
Jongmin Kim, Minsung Jeong, Jongyoon Han et al. (+1 more)
We present an efficient scheme to randomize a
spin-state ensemble in a nonlinear
spin-1 system by tuning chaos with an external periodic drive. Without modulation, the system exhibits a mixed phase space featuring regular islands embedded in a chaotic sea, where global mixing is inhibited by energy conservation. Using numerical simulations, we demonstrate that weak modulation of a linear Zeeman field not only facilitates transport between different energy shells but also drives ensembles toward a Haar-random distribution over
spin states. Under optimized conditions, complete randomization is achieved on a timescale set by the inverse nonlinear interaction energy. In the overdriven regime, randomization is unexpectedly suppressed at specific modulation amplitudes, accompanied by the formation of sticky regions in phase space. We attribute this behavior to the dynamical cancellation of the leading low-order harmonic component of the periodic drive. These results illustrate how time-periodic driving can be used to engineer chaotic systems and achieve controllable randomization in nonlinear
spin systems.
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All authors Jongmin Kim, Minsung Jeong, Jongyoon Han, Y. Shin
Quantum Gases · Cross-listed from quant-ph
Quantum Interference Amplifies Weak Chirality into Giant Quantum Nonreciprocity
Jing Tang and Yuangang Deng
Quantum nonreciprocity at few-
photon level typically requires strong
symmetry breaking, posing significant experimental challenges. Here we demonstrate that phase-controlled
quantum interference can amplify weak chirality into
giant quantum nonreciprocity. We consider two phase-programmable atoms coupled to a spinning whispering-gallery-mode resonator, where interference dramatically amplifies the effect of weak Fizeau splitting. This mechanism generates pronounced directional asymmetry in
photon statistics, featuring bright antibunched emission in one direction and strongly bunched emission in the opposite direction. Remarkably, both correlation and brightness isolations obey phase-controlled power-law scaling with Fizeau splitting, reaching up to 65~dB and 17.3~dB, respectively. Our results establish interference-enhanced weak chirality as a powerful route toward directional nonclassical light sources.
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Statistical Mechanics · Cross-listed from math.PR
Accelerated Simulation Algorithms for Extreme First-Passage Problems with General Emission Profiles
Emmanuel Akame Mfoumou and David Holcman
Fastest arrival events, where the first among many diffusing particles reaches a target, are central in triggering signal initiation in molecular
stochastic systems. Classical approaches to simulate such events rely on full trajectory generation of all particles, leading to prohibitive computational costs in the large particle number regime. In this work, we present a general simulation framework for efficiently generating order statistics of arrival times by exploiting asymptotic first-passage distributions. This framework applies to
diffusion processes in bounded domains with localized absorbing targets, for which short-time first-passage asymptotics are available, such as Brownian motion in dimensions one, two, and three. Starting with the case of instantaneous emission, we derive and implement a recursive inverse transform
algorithm to simulate the first $k$ arrivals without tracking particle trajectories. We extend this
algorithm to time-dependent emission profiles via an iterative approach, enabling the simulation of extreme statistics in systems with temporal injection, ranging from rapid to prolonged emission. Additionally, we provide asymptotic estimates of the mean fastest arrival time. To conclude, the present acceleration
algorithm which bypasses Brownian simulations of trajectories can be used for spatial reaction networks, rare event detection, or
diffusion-controlled activation.
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Statistical Mechanics · Cross-listed from math.PR
Exact Variance and Fano Factor for Arbitrary Level Crossings in Stationary Gaussian Processes
Shivang Rawat, Flaviano Morone, David J. Heeger et al. (+1 more)
Understanding the statistics of level crossings in
stochastic processes is crucial across many scientific disciplines. The traditional Kac-Rice formula gives the mean rate of level crossings and has found broad use. However, that mean rate captures only a coarse summary of the crossing process. It depends entirely on local properties of the
stochastic process at a given instant and is therefore blind to the correlation structure of the process over time. To understand whether crossing events, such as neuronal spikes, tend to cluster in time, spread apart, or exhibit more complex temporal organization, one must go beyond the mean rate and study higher-order crossing statistics. Here we go beyond the mean by deriving the exact analytical formulae for the variance and Fano factor of arbitrary level crossings in smooth stationary Gaussian processes. Our exact solution reveals how the full temporal correlation structure dictates whether crossings cluster or become regular. In systems with oscillatory correlations, such as a
stochastic damped harmonic oscillator, a recent crossing suppresses an immediate subsequent one, producing sub-Poissonian statistics. However, as damping increases and oscillations disappear, a large and slow excursion above the threshold can produce multiple closely spaced crossings, yielding super-Poissonian statistics. In purely relaxational, non-oscillatory systems, such as a mean-reverting process driven by Ornstein-Uhlenbeck noise, the competition between the timescales of the driving noise and system relaxation produces a richer landscape, including reentrant transitions between sub- and super-Poissonian statistics as the threshold level is varied. Taken together, the exact variance and Fano factor derived here complement the Kac-Rice mean rate, enabling more robust parameter estimation and model selection across any setting where Gaussian processes are used.
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All authors Shivang Rawat, Flaviano Morone, David J. Heeger, Stefano Martiniani
Materials Science
Thermal PBE in warm dense matter: Does it matter and is it accurate?
Kushal Ramakrishna, Mani Lokamani, Zhandos A. Moldabekov et al. (+3 more)
Conditional probability density functional theory has recently been used to derive the temperature dependence of the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) for the exchange-correlation (XC) free energy. We implement and systematically
benchmark thermal PBE within Kohn-Sham density functional theory calculations of warm dense matter. Comparisons with the local density approximation (LDA) and PBE functionals, as well as thermal LDA, show that thermal PBE significantly improves the description of warm dense matter properties, including energies, forces, pressures, and electronic charge densities. In particular, thermal PBE exhibits close agreement with path integral Monte Carlo (PIMC) reference data at negligible additional computational cost. This work demonstrates the practical utility of thermal PBE as an accurate semilocal functional for simulations in the warm dense regime.
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All authors Kushal Ramakrishna, Mani Lokamani, Zhandos A. Moldabekov, Tobias Dornheim, Kieron Burke, Attila Cangi
Strongly Correlated Electrons
Non-local low energy neutral excitations in a strongly disordered triangular Mott magnet Cr$_3$Se$_2$Br$_5$
Wenhao Liu, Dechen Zhang, Yuanqi Lyu et al. (+13 more)
Understanding if low-energy excitations can remain itinerant in the presence of strong disorder remains a central challenge in frustrated
quantum magnets, where disorder is generally expected to localize excitations through Anderson-like mechanisms. Here we report the emergence of charge-neutral itinerant excitations in a van der Waals compound Cr$_3$Se$_2$Br$_5$, a strongly disordered $S = 3/2$ Mott
insulator with a frustrated triangular
lattice. Structural analysis reveals substantial intrinsic disorder arising from Cr-site deficiency and Se/Br-site mixing, which appear to be fixed and cannot be readily tuned. No long-range
magnetic order or conventional glassy behavior is observed. In addition to its highly insulating nature, the
magnetic specific heat C_mag/T and thermal conductivity ąppa}_xx/T both exhibit linear temperature dependencies with substantial finite intercepts. In particular, a sizeable field-independent residual term $\kappa/T \approx 0.03~\mathrm{W\,m^{-1}\,K^{-2}}$ is observed, providing compelling evidence of itinerant low-energy excitations that carry
entropy without charge. These findings conceptually advance our understanding of
quantum matter by demonstrating a rare regime where the interplay of disorder, frustration, and electronic correlations actively reshapes the nature of low-energy excitations, allowing itinerant neutral excitations to coexist with strong intrinsic disorder.
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All authors Wenhao Liu, Dechen Zhang, Yuanqi Lyu, Lebing Chen, Lifang Hu, Keith M. Teddei, Yuting Zhang, Steve Shelton, Moon Kim, Xiqu Wang, Michael A. Susner, James G. Analytis, Dung-Hai Lee, Lu Li, Bing Lv, Robert J. Birgeneau
Materials Science
Imaging Surface Magnetization in Altermagnetic MnTe Films
Ling-Jie Zhou, Senlei Li, Zi-Jie Yan et al. (+15 more)
Altermagnets with pronounced
spin-splitting band structure, unconventional
magnetic and
crystal symmetries, and exotic magneto-transport properties have received immense interest in cutting-edge spintronics, materials science, and condensed matter physics research. Microscopic imaging of spontaneous
magnetic domains and phases in altermagnets constitutes an important step for investigating their underlying material properties, mechanisms, and
spin behaviors. Taking advantage of scanning-probe
quantum microscopy, here we report nanoscale
quantum sensing of a prototypical altermagnet candidate $\alpha$-MnTe. We visualize evanescent magnetization and the associated
magnetic domains in epitaxial MnTe films, which allows external
magnetic fields to control the intrinsic altermagnetic order and configurations. By evaluating a series of MnTe films with different thicknesses down to the atomic scale, we further present evidence for the interfacial origin of the observed weak magnetization and show its correlation with the anomalous
Hall effect in MnTe film. Our results advance the current understanding of emergent altermagnetism, providing insights into future material design of altermagnet-integrated spintronic devices.
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All authors Ling-Jie Zhou, Senlei Li, Zi-Jie Yan, Yufei Zhao, Hongtao Rong, Zelong Xiong, Yiran Zhao, Zhaorong Gu, Pu Xiao, Ke Wang, Lok Kan Lai, Hyeonhu Bae, Haoyu Liu, Chao-Xing Liu, Binghai Yan, Cui-Zu Chang, Hailong Wang, Chunhui Rita Du
Disordered Systems and Neural Networks · Cross-listed from physics.soc-ph
Local network evolution rules driving shortest path multiplicity
Alexei Vazquez
The shortest path multiplicity, here denoted by $\mu$, is an important metric of complex networks. For real networks $\mu$ is high and it correlates with the network community structure. Since local network
evolution induces network communities, it is possible that a high shortest path multiplicity is the natural expectation of local
evolution rules. Here I demonstrate, by means of numerical simulations and exact results, that this is indeed the case. For random graphs with arbitrary degree distributions $p_k$, $\langle\mu\rangle\sim \langle k(k-1)\rangle / (\langle k\rangle e)$, growing with the network size when $p_k\sim k^{-\gamma}$ and $\gamma\leq3$. For networks generated by
stochastic local rules, $\langle\mu\rangle$ increases with the network size and it does so faster than what is observed in their randomized versions. Furthermore, the number of communities increases with the network size and the correlation with $\langle \mu\rangle$ follows.
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Materials Science
Composition-Driven High-Entropy Alloys with Enhanced Magnetocaloric Properties
Nishant Tiwari, Juan Rafael Gomez Quispe, Noorbasha Bhavani Sai et al. (+4 more)
High
entropy alloys (HEAs) are promising magnetocaloric materials with tunable operating temperature conditions using compositional modifications. Here, we combine experiments and first principles based
spin modelling to engineer magnetocaloric response in single-phase cubic HEAs consisting of earth-abundant elements such as Fe, Ni, Co, Cr, and Cu. An equiatomic (Fe20Ni20Co20Cr20Cu20) and a Fe and Co rich non equiatomic (Fe34Ni17.7Co24.8Cr15.2Cu8.3) show a continuous
ferromagnetic to paramagnetic transition with Curie temperature (TC)=110 K and TC=420 K for non equiatomic. Under the 1.6 Tesla
magnetic field, the investigated
alloy shows the
entropy change =1.24 J per kgK with relative cooling power (RCP) =92 J per kg due to a broader effective cooling span. Density functional theory simulations reveal that reducing Cu enhances the
spin-polarized Fe, Co, or Ni, 3d weight near
fermi level, consistent with stronger
ferromagnetic exchange. Exchange couplings mapped onto a classical Heisenberg model and solved by atomistic Monte Carlo to theoretically predict TC of both the investigated
alloys. A controlled theoretical Cu sweep in equimolar further confirms that increasing Cu monotonically dilutes the
magnetic sublattice and lowers TC, providing a quantitative design guideline to tune magnetocaloric operating temperatures in transition metal HEAs.
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All authors Nishant Tiwari, Juan Rafael Gomez Quispe, Noorbasha Bhavani Sai, Saikat Talapatra, Pedro Alves Da Silva Autreto, Varun Chaudhary, Chandra Sekhar Tiwary
Strongly Correlated Electrons
Dynamical susceptibility and quantum Fisher information in the Su-Schrieffer-Heeger model with Hatsugai-Kohmoto interactions
Sepide Mohamadi and Jahanfar Abouie
We investigate the dynamical
spin and charge susceptibilities and the associated
quantum Fisher information in a class of interacting
lattice models, with a primary focus on the Su-Schrieffer-Heeger model in the presence of Hatsugai-Kohmoto interactions. To provide a rigorous analytical
benchmark, we contrast the response properties of the SSH-HK system with those of the single-band Hubbard and SSH-Hubbard models, treated within the random-phase approximation. While standard Hubbard-type interactions typically suppress excitation strength, we demonstrate that the SSH-HK model displays qualitatively distinct physical behavior arising from the interplay between SSH dimerization and the momentum-diagonal nature of the HK interaction. Leveraging the exact solvability of the HK term, we derive closed-form expressions for the dynamical susceptibility, revealing unique filling-controlled characteristics such as a finite response at zero wave vector and a pronounced restructuring of spectral weight across integer and fractional filling sectors. We show that the
quantum Fisher information, defined as the frequency integral of the imaginary part of the susceptibility, serves as an efficient probe of these filling sectors, exhibiting distinct piecewise behavior that distinguishes integer from fractional fillings. Notably, our results indicate that the
quantum Fisher information remains insensitive to topological transitions within uniform-density regimes, highlighting the limitations of standard dynamical response functions in characterizing band
topology. These findings establish the SSH-HK model as a powerful analytical platform for exploring the competition between
topology and strong correlations, demonstrating how dynamical susceptibilities and the
quantum Fisher information provide complementary, experimentally accessible probes of many-body physics.
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Materials Science
Exploring Multi-Transition-Metal NASICON Frameworks as High-Performance Cathodes for Sodium-Ion Batteries
Santosh Behara, Achinthya Krishna Bheemaguli and Gopalakrishnan Sai Gautam
The search for sustainable, high-performance cathodes has driven a growing interest in sodium superionic conductor (NASICON)-type phosphates for sodium-ion batteries (SIBs). To identify promising NASICONs containing earth-abundant transition metals (TMs) and to systematically examine the role of multiple TMs in influencing the various properties of NASICON cathodes, we employ density functional theory calculations to investigate nine NASICON compositions containing Mn, Cr, and/or Fe, and spanning unary, binary, and ternary combinations. Our calculations reveal that unary systems, in terms of their Na intercalation phase behavior, exhibit well-defined stabilization at intermediate Na contents ($x$ in Na$_x$TM$_2$(PO$_4$)$_3$), while binary and ternary systems display more complex phase behavior, with some systems showing a shift of thermodynamic minima from $x$ = 3 to 2. Intercalation voltages highlight the dominant role of Fe$^{4+}$/Fe$^{3+}$ redox activity in elevating average voltages ($\sim$4.0 V), while Mn and Cr introduce intermediate-to-low voltage redox activity. Electronic structure data demonstrate non-systematic changes in the band gap, especially in systems containing multiple TMs. Na$^+$ mobility results identify mixed-TM frameworks as favorable, achieving Na$^+$ migration barriers in the 0.3-0.4 eV range. Importantly, we identify Na$_x$MnFe$_{0.5}$Cr$_{0.5}$(PO$_4$)$_3$ to be a promising ternary composition for subsequent experimental validation, offering an optimal intersection of phase stability, voltages, thermodynamic (meta)stability, and Na$^+$ migration barriers. Together, our study provides fundamental insights into the interplay between compositional complexity, thermodynamic stability, electronic structure, and ionic transport in NASICONs, and offers actionable design principles for utilising multi-TM NASICONs as high performance SIB cathodes.
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Statistical Mechanics
First-passage time distribution of a Brownian particle harmonically confined in a viscoelastic bath
Brandon R. Ferrer and Juan Ruben Gomez-Solano
We investigate theoretically and experimentally the first passage-time properties of a spherical Brownian particle that is harmonically trapped at thermal
equilibrium in a fluid at constant temperature. By using the overdamped version of the generalized Langevin equation, we derive a general expression for the probability density function of the time that the particle takes to reach for the first time the minimum of the potential starting from an arbitrary position. We show that such a first-passage time distribution can be implicitly expressed in terms of the friction
memory kernel that encodes the interaction of the particle with its surroundings, and correctly reduces to previously found expressions in the case of a Markovian viscous bath. We validate our theoretical results by measuring the first-passage time of colloidal beads optically trapped in non-Markovian baths such as viscoelastic
polymer and micellar solutions, as well as in a viscous glycerol/water mixture and water, which behave as Markovian media, having quantitative agreement with the derived expressions. In particular, we find that the mean first-passage time in a viscoelastic bath can surpass that in a viscous medium of the same zero-shear viscosity due to the emergence of slowly decaying tails in the first-passage time probability density of the former.
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Quantum Gases
Lattice polarons with extended interactions
Enrique I. Ramírez-Juárez, Genaro Lopez-Olivera, Luis A. Peña Ardila et al. (+1 more)
Lattice impurities have recently emerged as a platform in which polarons unveil new
quantum many-body states absent in free space and can serve to probe strongly correlated matter. In this work, we investigate two-dimensional
lattice polarons with strong on-site repulsion and tunable nearest-neighbor interactions using a variational approach including up to one excitation of the medium. We show that extended interactions qualitatively modify the quasiparticle structure beyond the conventional attractive and repulsive polaron picture. A direct analysis of the
eigenvalue spectrum reveals the presence of dark
impurity states, orthogonal to the bare
impurity and therefore spectroscopically dark. These states exhibit nontrivial internal structure, including dipolar
symmetries in real space. Our results demonstrate that long-range interactions generate multiple quasiparticle excitations with distinct
symmetry properties, highlighting the crucial role of interaction range and
lattice geometry. This work opens new avenues for probing hidden quasiparticle states in
lattice systems through spectroscopic and wave-function-resolved measurements.
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All authors Enrique I. Ramírez-Juárez, Genaro Lopez-Olivera, Luis A. Peña Ardila, Arturo Camacho-Guardian
Superconductivity
Light-Driven Intrinsic Perfect Superconducting Diode Effect
Makoto Ichikawa and Youichi Yanase
We demonstrate the perfect superconducting diode effect (SDE) – unidirectional supercurrent with 100% diode efficiency – in light-driven nonequilibrium systems. Although the perfect SDE is difficult to achieve in
equilibrium, monochromatic light induces the perfect SDE in systems lacking inversion and time-reversal
symmetries. More strikingly, multi-frequency light enables the perfect SDE even in centrosymmetric systems via dynamical
symmetry breaking. Our results establish a general principle for realizing unidirectional superconducting transport based on nonequilibrium control and
symmetry engineering.
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Soft Condensed Matter
Unfrustrated Self-Morphing of Bulk Liquid Crystal Elastomers
Shachaf Rotem and Hillel Aharoni
Precise manipulation of shape-morphing responsive materials is crucial for applications in soft robotics and adaptive structures. While notable precision has been achieved in thin two-dimensional sheets, an accurate volumetric shape-morphing remains a major challenge due to
geometric frustration, which inevitably generates complex, residual elastic stresses. In this work, we extend the
geometric approach used for thin sheets to bulk
Liquid Crystal Elastomers (LCEs). By examining their reference
Ricci curvature, we formulate the minimal set of conditions required for a three-dimensional nematic director field to undergo stress-free, frustration-free deformations upon actuation. Through this mathematical framework, we identify two distinct classes of geometrically compatible bulk systems. The first class comprises twistless director fields that remain frustration-free across all temperatures, leading to
holographic design principles demonstrated through "Planar" and "Smectic" LCE subfamilies. The second class features twisted configurations that exhibit unique, temperature-selective compatibility, leading to non-monotonic accumulation of internal elastic stresses that relax completely at a predefined target temperature. Our framework establishes a firm mathematical foundation for robust forward and inverse design protocols in bulk LCEs.
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Materials Science
First-principles finite-size correction schemes for point defects of Cu$_3$N
Abdul M. Reyes, Sebastian E. Reyes-Lillo and Eduardo Menéndez-Proupin
Point defects play a key role in determining
semiconductor properties, such as electrical conductivity and photoluminescence, and often enable functional behavior. Accurate first-principles supercell simulations of point defects require reliable finite-size corrections. In this study, we combine PBE+U structural relaxations with HSE hybrid-functional calculations to determine defect formation energies and thermodynamic transition levels of Cu$_3$N. Finite-size trends are quantified using $\Gamma$-point calculations in supercells containing 256, 864, and 2048 atoms. We assess and extend the Makov-Payne and Lany-Zunger correction schemes by introducing additional $1/L^n$ terms, together with core-level potential
alignment and defect-specific scaling models. Using Cu$_3$N as a case study, we show that charged vacancies with strongly localized defect states are accurately described by the Makov-Payne-type scaling ($1/L + 1/L^{3}$), whereas interstitial defects with shallow or weakly localized electronic character are better captured by a hydrogenic
impurity model that accounts for defect-band dispersion. Residual trends for neutral or weakly localized defects are described by higher-order
polynomial fits in $1/L^{3}$ and $1/L^{4}$. Hybrid-functional energetics corrected using PBE+U-based finite-size trends confirm the intrinsic $p$-type character of Cu$_3$N under the conditions considered and demonstrate that no single finite-size correction can be transferred across all defect types.
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Statistical Mechanics
A particle-resolved rheological study of chirality transfer and odd transport
Rémi Goerlich, Alexander P. Antonov, Kristian Stølevik Olsen et al. (+4 more)
Chirality, or the breaking of mirror
symmetry, appears across all scales in nature, from molecular conformations to the dynamics of bacterial collectives. Environments composed of such
symmetry-breaking constituents can give rise to emergent physical phenomena, particularly in the transport and response of embedded tracers. Yet it remains unclear how
chiral environments influence such tracers and through which microscopic mechanisms anomalous responses emerge. Here, we present a particle-resolved study of these systems, demonstrating chirality transfer and odd transport of an object embedded in a
chiral active bath. In a rheological experiment, a symmetric passive tracer is driven through collisions with the particles of a non-
equilibrium chiral bath. Combining table-top experiments, many-body simulations, and a reduced coarse-grained theory, we demonstrate that local collisions transfer
chiral active dynamics to the tracer, which displays circular trajectories. We show that the same mechanism gives rise to a systematic transverse drift under a constant pulling force. Crucially, we identify nonlinear friction as an essential factor that rectifies these transferred
chiral active fluctuations into a macroscopic odd response. Our results reveal a microscopic mechanism for odd transport in
chiral active matter and provide general insights into transverse transport in driven non-
equilibrium systems.
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All authors Rémi Goerlich, Alexander P. Antonov, Kristian Stølevik Olsen, Lorenzo Caprini, Christian Scholz, Hartmut Löwen, Yael Roichman
Materials Science
Harmonic Hierarchy of Altermagnetic Spin Splitting from Symmetry-Adapted Wavefunctions
Yixuan Che, Peibo Xu, Haifeng Lv et al. (+2 more)
Altermagnets combine
magnetic compensation with
spin-momentum-locked splitting in the absence of
spin-orbit coupling, yet existing descriptions, formulated primarily in terms of
spin symmetry and
lattice geometry, provide limited insight into the electric-structure perspective of its angular harmonic form. Here, we identify a wavefunction-level framework for altermagnetism in two-dimensional square
lattices. Using
symmetry-adapted
polynomial wavefunctions, we show that the harmonic structure of momentum-space
spin splitting is inherited from the geometry of the electronic wavefunctions which can be selected by
crystal fields. Identical orbital sectors preserve conventional
antiferromagnetic degeneracy, whereas intertwined linear and quadratic wavefunctions generate d-wave and g-wave altermagnetic anisotropies, respectively. Tight-binding analysis connects this hierarchy to inequivalent same-
spin hopping channels. First-principles calculations on the g-wave mcm-type reticular material platforms confirm high-
symmetry-linear degeneracy together with finite generic-k splitting. Our results establish a hierarchy linking wavefunction geometry, orbital realization, microscopic hopping anisotropy, and altermagnetic electronic structure.
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All authors Yixuan Che, Peibo Xu, Haifeng Lv, Xiaojun Wu, Jinlong Yang
Mesoscale and Nanoscale Physics
Intrinsic Topological Control of the Orbital Hall Effect in Buckled Dirac Materials
Madiha Zia, Muzamil Shah, Kashif Sabeeh et al. (+2 more)
We study the orbital
Hall response in buckled two-dimensional Dirac materials using a unified framework that includes an
antiferromagnetic exchange field, a perpendicular electric field, and intrinsic
spin-orbit coupling. We show that the orbital
Hall conductivity is considerably boosted around band-inversion points and shows different signatures across multiple electronic phases using a low-energy massive Dirac model in conjunction with Berry-
curvature-based linear response theory. We find a series of
quantum spin Hall, valley
Hall, and anomalous
Hall regimes by methodically adjusting external fields, and demonstrate how the
evolution of the orbital response is controlled by the redistribution of Berry
curvature between
spin and valley sectors. We examine the impacts of finite temperature in more detail and find that although the response s size is suppressed by thermal broadening, the distinctive phase-dependent features remain robust. Our findings demonstrate that orbital
Hall conductivity offers a sensitive band
topology probe in Dirac systems and emphasize buckled two-dimensional materials as a flexible platform for engineering tunable orbital currents for orbitronic applications.
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All authors Madiha Zia, Muzamil Shah, Kashif Sabeeh, Gao Xianlong, Reza Asgari
Mesoscale and Nanoscale Physics
Cascaded Four-Wave Mixing on Quantum Paraelectrics for On-chip Cryogenic Microcombs
Harikrishnan Sundaresan, Prasad Muragesh and Madhu Thalakulam
Here, we demonstrate an on-chip cryogenic microwave frequency-comb on a planar superconducting resonator fabricated on Strontium titanate(STO), a
quantum paraelectric material. The material's Kerr-type nonlinearity arising from the
quantum paraelectric phase, an underexplored state, enables pronounced resonance shifts, Duffing-like bifurcations and comb generation via cascaded foure-wave mixing. Our results establish STO resonators as a low power, cryogenically compatible platforms for nonlinear microwave photonics, with applications in scalable
quantum control and on-chip frequency synthesis.
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