Mesoscale and Nanoscale Physics
Localized Excitonic Emission in Wafer-Scale MOCVD-Grown GaSe 2D Nanosheets for Classical and Non-Classical Light Sources
Bhabani Sankar Sahoo, Nils Fritjof Langlotz, Shachi Machchhar et al. (+11 more)
Wafer-scale growth of two-dimensional
semiconductors remains a key challenge for their integration into photonic technologies. While most studies of two-dimensional
semiconductors have focused on transition metal dichalcogenides and their scalable fabrication, comparatively little
attention has been given to III-VI monochalcogenides. Here, we report wafer-scale growth of gallium selenide (GaSe) by metal-organic chemical vapor deposition (MOCVD) and investigate its structural and optical properties for visible-range classical and
quantum light emission. Two samples with thicknesses ranging from a few monolayers to several micrometers, controlled via the growth time, were investigated. The 30-minute grown sample yields intense, broad photoluminescence spanning 1.7–2.0$\,$eV, whereas the thinner 3-minute sample exhibits discrete narrow emission lines and single-
photon emission with $(g^{(2)}(0) = 0.15 \pm 0.10)$. Remarkably, cathodoluminescence mapping reveals pronounced spatial localization of both spectrally narrow and broad emission centers. Together with temperature-dependent power-law analysis and Raman mapping, our results indicate defect-induced emission rather than intrinsic excitonic recombination. These findings establish wafer-scale MOCVD grown 2D GaSe as a platform for classical and non-classical light sources and highlight defect-engineered localization as a route toward scalable
quantum photonics.
Read the full abstract ▾
All authors Bhabani Sankar Sahoo, Nils Fritjof Langlotz, Shachi Machchhar, Kartik Gaur, Robin Günkel, Max Bergmann, Naghmeh Ghadghooni, Aris Koulas-Simos, Jürgen Belz, Chirag Chandrakant Palekar, Maximilian Ries, Kerstin Volz, Stephan Reitzenstein, Imad Limame
Mesoscale and Nanoscale Physics
Selective Fermi-Level Pinning: A Design Strategy for Giant Rectification in Molecular Junctions
Junnan Guo, Wenhui Fang, Jian Huang et al. (+3 more)
Molecular rectifiers are key functional components of molecular-scale integrated
circuits, yet achieving high rectification ratios remains a longstanding challenge due to the intrinsic
symmetry of resonant tunneling and the complexity of interfacial energy-level
alignment. Here, we propose a rectifier design strategy based on selective
Fermi-level pinning that breaks transport
symmetry via pinning interactions between molecular frontier orbitals and electrodes. This framework enforces tunneling transport to be predominantly governed by unoccupied molecular orbitals, while substantially suppressing contributions from occupied states, thereby establishing a simplified and highly controllable rectification mechanism. The resulting cyclo[n]carbon-based molecular junctions exhibit
giant rectification ratios exceeding 103, while retaining exceptional structural robustness against variations in both donor chain length and carbon ring size. This work reveals the critical role of selective
Fermi-level pinning in molecular junctions and provides a general design principle for engineering functional single-molecule electronic devices.
Read the full abstract ▾
All authors Junnan Guo, Wenhui Fang, Jian Huang, Weikang Wu, Hui Li, Lishu Zhang
Statistical Mechanics
Inviscid scaling in the Kuramoto-Sivashinsky equation from functional renormalization group and direct numerical simulations
Liubov Gosteva, Dipankar Roy, Nicolás Wschebor et al. (+1 more)
We show that the one-dimensional Kuramoto-Sivashinsky (KS) equation features a scaling regime characterized by the dynamical exponent $z=1$ at intermediate scales between the large-scale Kardar-Parisi-Zhang (KPZ) scaling with $z=3/2$ and the small-scale non-universal behavior. This scaling regime is intrinsic to the KS dynamics since it arises from the vanishing of the effective viscosity when evolving from its microscopic negative KS value, to its macroscopic effective positive KPZ value. This vanishing of the viscosity deeply imprints the behavior of correlations at intermediate scales, which exhibit a universal $z=1$ scaling. This behavior pertains to the inviscid-Burgers universality class, which corresponds to the zero-viscosity fixed point of the KPZ equation. We evidence and characterize this so-far-overlooked scaling regime using both functional renormalization group and direct numerical simulations.
Read the full abstract ▾
All authors Liubov Gosteva, Dipankar Roy, Nicolás Wschebor, Léonie Canet
Strongly Correlated Electrons
S.D. Nabi, E. Ressouche, D. G. Mazzone et al. (+5 more)
We report
neutron diffraction under applied
magnetic fields and complementary zero-field
neutron spectroscopy measurements on Cs$_2$RuO$_4$. Previous work [S. D. Nabi et al., Phys. Rev. B 112, 134436 (2025)] identified a
spin-flop-like transition accompanied by a
quantum critical point within the ordered phase, attributed to strong frustration between alternating single-ion anisotropy planes. Here, we quantitatively confirm the predicted field
evolution of the
magnetic structure using
neutron diffraction. Furthermore, analysis of the excitation spectrum within an SU(3)
spin-wave framework resolves previously undetermined parameters of the minimal
spin Hamiltonian and lifts the associated degeneracies.
Read the full abstract ▾
All authors S.D. Nabi, E. Ressouche, D. G. Mazzone, J. Lass, R. Sibille, Z. Yan, S. Gvasaliya, A. Zheludev
Materials Science
A Metadynamics-Based Framework for Free Energy Surface Mapping of Multiparticle Diffusion in Crystals
Shunya Yamada and Kazuaki Toyoura
We propose two metadynamics (MetaD)-based methodologies for efficiently mapping free energy surfaces (FESs) of multiple interacting carriers diffusing in crystalline solids. Our approaches circumvent the challenges of high-dimensional collective variables (CVs) by employing replica state exchange MetaD and parallel bias MetaD, both of which decompose the high-dimensional CVs into multiple lower-dimensional ones. As a
benchmark, we investigate two-dimensional lithium (Li)
diffusion in LixTiS2 across a wide range of Li concentrations. The Li jump frequencies estimated from the obtained FESs exhibit concentration- and temperature-dependent trends consistent with previous kinetic Monte Carlo simulations and
nuclear magnetic resonance measurements. Our approaches provide a promising framework for capturing the slow dynamics of diffusive carriers that are typically inaccessible to conventional molecular dynamics simulations.
Read the full abstract ▾
Materials Science
Cathodoluminescence Analysis of Defects and Grain Boundaries in Zn3P2 Thin Films Grown on Graphene by MOVPE and MBE
Thomas Hagger, Mohammadreza Hassanzadeh, Aidas Urbonavicius et al. (+12 more)
Zn3P2 is a promising earth-abundant absorber for thin-film photovoltaics, yet its development is hindered by the lack of
lattice-matched substrates, its incompatible thermal expansion coefficient, and a complex defect landscape. Here, we demonstrate the quasi-van der Waals epitaxy of Zn3P2 on
graphene by metal-organic vapour phase epitaxy (MOVPE) and directly link the density of antiphase boundaries to optical emission modulation using correlative electron microscopy and cathodoluminescence (CL). Moreover, it is observed through CL that grain boundaries act as non-radiative sinks for excited charge carriers. The effect extends several micrometres into the grains, making grain boundaries detrimental to the applicability of Zn3P2 in read devices. Further comparison with molecular beam epitaxy grown films reveals the suppression of strain-related sub-bandgap emission in MOVPE-grown material. Overall, quasi-van der Waals epitaxy of Zn3P2 by MOVPE resulted in larger grains and improved material quality. In addition, these results directly link extended defects to recombination pathways in Zn3P2 and highlight grain-size control as a key strategy for improving earth-abundant photovoltaic absorbers.
Read the full abstract ▾
All authors Thomas Hagger, Mohammadreza Hassanzadeh, Aidas Urbonavicius, Ahmed El Alouani, Victor Boureau, Gulnaz Ganeeva, Nico Kawashima, Raphael Lemerle, Kamil Arthur Wodzislawski, Sebastian Lehmann, Kimberly A. Dick, Silvana Botti, Adrien Michon, Anna Fontcuberta i Morral, Simon Escobar Steinvall
Materials Science
Studying Creep-Fatigue interaction of Nickel-Based Superalloys using Crystal Plasticity and Entropy-Based life prediction model
Santosh Kumar Shaw, Sabyasachi Chatterjee, Alankar Alankar et al. (+1 more)
Creep-fatigue interaction in single-
crystal nickel superalloys is difficult to predict because the response depends on the combined effects of loading parameters, hold time, temperature, and the underlying deformation mechanisms. This is important for turbine blade applications, where components experience both fatigue and creep during service. In the present work, a
crystal plasticity finite element (CPFE) framework is used to study the creep-fatigue response of a single-
crystal nickel superalloy under a range of practically relevant thermo-mechanical loading conditions. In particular, the effects of strain amplitude, R-ratio, hold duration, and temperature on cyclic deformation, stress relaxation, damage
evolution, and creep-fatigue life are examined. Particular
attention is given to separate the roles of fatigue and creep damage, understanding their interaction, and identify the creep-dominated and fatigue-dominated regimes as a function of strain amplitude and hold time. The study brings together these effects within a single framework and shows that the predicted trends in cyclic response and life are in good agreement with experimental observations reported in the literature.
Read the full abstract ▾
All authors Santosh Kumar Shaw, Sabyasachi Chatterjee, Alankar Alankar, Ayan Bhowmik
Soft Condensed Matter
Orientational frustration drives enhanced diffusion of anisotropic particles in a liquid labyrinth
Rohit Mangalwedhekar, Limeng Ruan, Somen Nandi et al. (+5 more)
Transport of nanoscale objects in complex, structured environments plays a key role in a wide range of processes, from biomolecular dynamics in extracellular spaces to transport in porous materials such as filters and catalysts. While anomalous
diffusion is well established, how particle anisotropy governs transport under
geometric constraints remains unclear. Here we use 3D single-particle tracking to investigate the
diffusion of stiff one-dimensional carbon nanotubes in a continuous soft matter network of interconnected chambers and constrictions. Transport is anomalous and antipersistent, with strong length dependent confinement and trapping, consistent with obstructed
diffusion. Unexpectedly, however, escape from confinement is poorly sensitive to nanotube length as opposed to what would be expected of pore mediated transport. Despite a tenfold length increase and significantly enhanced trapping, escape time increased by only ~1.4. Single-particle orientational tracking reveals the origin of this weak scaling. Indeed, long nanotube, i.e. those with length comparable to the chamber dimensions, dynamically align with constrictions enabling efficient, geometry-assisted escape that offsets increased confinement while shorter nanotubes need to screen the volume to find their escape path. These results uncover an
alignment-mediated transport mechanism that decouples confinement strength from escape kinetics, distinct from pore-mediated transport mechanisms, establishing a quantitative framework for anisotropic
diffusion in complex environments.
Read the full abstract ▾
All authors Rohit Mangalwedhekar, Limeng Ruan, Somen Nandi, Quentin Gresil, Marc Tondusson, Stephane Bancelin, Lea-Laetitia Pontani, Laurent Cognet
Soft Condensed Matter
Memory-driven topological ordering during the transition from dormant to migrating epithelia
Richard Ho, Anna Lång, Emma Lång et al. (+2 more)
Transitions from quiescence to collective migration in epithelia underlie wound healing and cancer invasion, yet their physical origin remains poorly understood. Here we show that quiescent epithelial monolayers store spatially contractile stresses that function as a form of mechanical
memory. Upon serum-induced reactivation, these pre-stressed regions nucleate extensile asters that emit propagating polarity domain walls. Along these interfaces, topological defects are created, advected and annihilated, leading to defect coarsening with faster kinetics than by elastic interactions. An active elastic model quantitatively reproduces the observed dynamics and identifies stored stress as the origin of rapid topological reorganization. Our results establish a mechanism in which mechanical
memory in quiescent epithelia triggers active stress release, driving collective migration via rapid topological ordering, distinct from conventional unjamming and flocking transitions.
Read the full abstract ▾
All authors Richard Ho, Anna Lång, Emma Lång, Stig Ove Bøe, Luiza Angheluta
Other Condensed Matter · Cross-listed from quant-ph
Quantum viscosity mechanism of the dissipative dynamics in the Dicke model expressed via Lindblad equation of motion
M.E.S.Beck, S.S.Seidov and S.I.Muhkin
Quantum dissipation is studied in the superradiant phase of the Extended Dicke model. It is demonstrated analytically by
quantum mechanical derivation of the Lindblad equation for the Dicke model in the superradiant state coupled to Caldeira-Leggett thermal bath, that the effective viscosity appearing in the semiclassical equations of motion of polaritonic condensate survives in the zero temperature limit T -> 0. The nonzero contribution to viscosity contains prefactor nB ({\omega}, T ) + 1 with the Bose-Einstein function nB of harmonic oscillators in the thermal bath, indicating that virtual excitations of harmonic oscillators in the thermal bath coupled to the polaritons of Dicke model give rise to effective viscosity in the T -> 0 limit. Besides, it is demonstrated analytically, that correct expression for Lindbladian in the superradiant phase should be built using condensate-shifted creation and annihilation operators of the
photons and pseudospin operators in Holstein-Primakoff representation of the coupled to
photons two-level systems in order the system could relax to its minimum energy in T -> 0 limit due to thermal bath provided effective viscosity.
Read the full abstract ▾
Materials Science
Thermodynamic stability of twisted domains in AgCrSe$_{2}$ thin films grown on lattice-matched YSZ(111) substrate
Haruto Sato, Kota Mihara, Kenshin Inamura et al. (+4 more)
Control of structural domains in epitaxial thin films of functional materials is a fundamental technique to utilize their intrinsic physical and chemical properties in solid-state devices. In this study, we report on suppression of twisted-domain formation in thin-film growth of polar
magnetic semiconductor AgCrSe$_{2}$ using pulsed-
laser deposition. In exploring concomitant optimized growth temperature and Ag/Cr composition ratio of supply, we find the critical growth temperature ($T\mathrm{_{sub}}$) for obtaining single 60$^{\circ}$ domain in c-axis oriented AgCrSe$_{2}$ thin film on a
lattice-matched (111) plane of the yttria-stabilized zirconia substrate. At temperatures below and above the critical $T\mathrm{_{sub}}$, metastable 0$^{\circ}$ domain in addition to the 60$^{\circ}$ domain emerges, indicating delicate energy balance of thermodynamic stability for obtaining the single-domain structure. Surface structural analysis using time-of-flight low-energy atom scattering spectroscopy reveals the presence of two polar orientations along $+Z$ and $-Z$ directions. These findings provide valuable insights into the thin-film growth mechanisms for a family of two-dimensional compounds with rhombohedral
lattices.
Read the full abstract ▾
All authors Haruto Sato, Kota Mihara, Kenshin Inamura, Yusuke Tajima, Kazutaka Kudo, Jobu Matsuno, Junichi Shiogai
Statistical Mechanics · Cross-listed from cs.LG
Reinforcement Learning for Graph Generation under a Hard Assortativity Constraint
Hoyun Choi, Junghyo Jo and Deok-Sun Lee
Generating graph ensembles with precisely controlled structural properties is central to investigating how network structure shapes function. Canonical ensembles impose constraints only in expectation (soft constraints), letting individual realizations fluctuate around the target, whereas enforcing hard constraints with prescribed precision in every realization remains challenging beyond fixing the degree sequence. Here we show that a reinforcement learning framework can drive a graph through degree-preserving rewirings to satisfy a prescribed assortativity, which characterizes the degree–degree correlation of adjacent nodes. By replacing the entropically dominated Metropolis–Hastings random walk with directed transport, the learned policy reduces generation cost by at least an order of magnitude while retaining over 98% of configurational diversity. Trained on small graphs, the framework generalizes across sizes and
topologies without retraining, enabling quantitative isolation of secondary observables such as the clustering coefficient. These results establish reinforcement learning as a practical paradigm for hard-constrained graph generation.
Read the full abstract ▾
Materials Science
In situ estimation of local acoustic pressure amplitude by force balancing with a ferrofluid droplet probe
Seiya Usui, Yoshiaki Uchida, Akira Nagakubo et al. (+1 more)
Acoustic tweezers enable non-contact manipulation of microscale objects, but quantitative in situ evaluation of the peak local pressure amplitude remains difficult in confined devices. Conventional hydrophone-based measurements are often limited at the microscale by probe size and installation constraints. Here, we present a force-balance method in which a trapped ferrofluid droplet serves as a local probe in a standing-wave acoustic field and an externally applied
magnetic-field gradient is tuned so that the
magnetic force balances the maximum primary acoustic radiation force on the droplet. From the
magnetic force on the ferrofluid droplet, determined at the balance point, we estimate a peak local pressure amplitude of $2.2\times10^{5}$~Pa for 7.2~MHz operation at 10~V$_{\mathrm{pp}}$. This approach provides a practical route for quantitative in situ characterization of microscale acoustic fields and for setting operating conditions in compact acoustofluidic devices.
Read the full abstract ▾
All authors Seiya Usui, Yoshiaki Uchida, Akira Nagakubo, Norikazu Nishiyama
Quantum Gases
Quantum fluctuations in a quartet superfluid of two-dimensional Fermi mixture
Wei Wang, Yupeng Wang and Xiaoling Cui
We study
quantum fluctuations in a quartet superfluid (QSF) of two-dimensional (2D)
fermion mixtures with mass imbalance. Here QSF is a high-order superfluid that corresponds to the condensation of ($1+3$) clusters, each consisting of a light
fermion and three heavy ones. By incorporating the Gaussian fluctuations respecting dominant four-body correlations in this system, our theory successfully recovers the leading universal logarithmic contribution to the 2D equation of state in the deep binding regime, thereby offering a correct physical picture of quartet clusters behaving as composite
bosons. By extending the Gaussian fluctuation theory from pairing to quartet superfluids, our results shed light on
quantum fluctuations in general
fermion superfluids with arbitrarily high-order correlations.
Read the full abstract ▾
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Interference of local-measurement histories
Parveen Kumar, Igor V. Gornyi and Yuval Gefen
The
evolution of a
quantum system comprises two fundamental processes–continuous
unitary dynamics and
stochastic measurement-induced jumps. The latter are often viewed as a source of decoherence. Can two histories of such an
evolution, made up of local measurements, interfere with each other? Here, we answer this question in the affirmative. A manifestation of this interference is the generation of
entanglement between two parts of the system that are individually coupled to distinct detectors. Specifically, we develop a protocol in which two alternative local measurement processes act on a pair of
qubits, and show how interference of histories is generated under coherent control, leading to
entanglement. Furthermore, we find that averaging over the detectors' readouts still results in an entangled (albeit not maximally entangled) state. Our results extend the notion of
quantum interference beyond
unitary evolution to genuinely measurement-driven dynamics, and identify limits on the generation of
quantum correlations using interference of measurement histories.
Read the full abstract ▾
Statistical Mechanics
Exact solution of generalized gauge-invariant Ising chains with multi-spin interactions
Pavel Khrapov and Stepan Shchurenkov
In this work, exact solutions are obtained for a class of generalized gauge-invariant $n$-chain Ising models ($n=1,2,3,4$) with arbitrary multi-
spin interactions that are invariant under the local $\mathbb{Z}_2$ gauge group. On a strip
lattice of finite length $L$ and width $n$ with periodic or free boundary conditions, an explicit expression for the partition function is derived using the transfer-
matrix method. Two successive transformations are developed: elimination of gauge redundancy and reduction of the original model to an effective $n$-chain Ising model with all possible interactions between neighboring vertical layers. On the basis of the spectral decomposition of the $2^n\times 2^n$ transfer
matrix, general formulas are obtained for gauge-invariant correlation functions and Wilson loops of arbitrary width. For $n \le 3$, explicit expressions are derived in terms of
eigenvalues and eigenvectors. A detailed analysis of the behavior of the Wilson loop is performed, which allows us to identify regimes exhibiting area-law (confinement-like) and perimeter-law (deconfinement-like) dependence. For specific
Hamiltonians, the string tension is computed and the corresponding phase diagrams are constructed. The results generalize and substantially extend the classical works on the gauge-invariant Ising model.
Read the full abstract ▾
Materials Science
Non-adiabatic phonon renormalization in metallic versus insulating rutile oxides
Reshma Kumawat, Shubham Farswan, Simranjeet Kaur et al. (+1 more)
We present a comparative Raman scattering study of metallic rutile
oxides (RuO$_2$ and IrO$_2$) and insulating rutiles (TiO$_2$ and SnO$_2$). Temperature-dependent Raman spectra reveal that the metallic compounds exhibit pronounced
phonon frequency hardening, $\omega(11~\mathrm{K})-\omega(300~\mathrm{K})=\Delta\omega \approx 6$-$10~\mathrm{cm}^{-1}$, whereas the insulating rutiles show only modest hardening, $\Delta\omega \approx 1$-$3~\mathrm{cm}^{-1}$. In contrast, the linewidth changes, $\Delta\Gamma \approx 1$–$7~\mathrm{cm}^{-1}$, do not display a systematic metallic-insulating classification. Fits with the conventional Klemens anharmonic decay model reproduce the overall temperature trends but yield inconsistent anharmonic parameters for the metallic compounds when benchmarked against insulating rutile analogues. A modified Klemens framework, incorporating an additional $T^{2}$ correction to the
phonon frequency arising from the electronic contribution to the
phonon self-energy, quantitatively accounts for the enhanced renormalization observed in metallic systems. These results establish finite non-adiabatic electron-
phonon coupling in metallic rutiles and demonstrate that
phonon renormalization can be identified even in the absence of observable Fano asymmetry in the
phonon line shapes.
Read the full abstract ▾
All authors Reshma Kumawat, Shubham Farswan, Simranjeet Kaur, Kaushik Sen
Materials Science · Cross-listed from quant-ph
Transition-state lattice modes and the breakdown of adiabatic tunneling for hydrogen and deuterium in bcc Nb
P. Graham Pritchard and James M. Rondinelli
Interstitial hydrogen and deuterium in body-centered-cubic metals constitute archetypal
quantum tunneling systems. Their relevance has been renewed by the connection between hydrogenic tunneling in Nb and defect-induced decoherence in superconducting
qubits, motivating a predictive microscopic theory. Existing theoretical treatments invoke an adiabatic separation between the light interstitial and the host
lattice, an assumption whose validity has not been rigorously established for hydrogenic species. Here, we show that the experimentally measured tunnel splittings of O-trapped H and D in bcc Nb are quantitatively well-described within a five-dimensional (5D)
Lattice-Renormalized Born-Oppenheimer (LRBO) framework. This approach treats three interstitial modes and two judiciously selected
lattice modes, which includes a transition-state mode, on equal
quantum footing. By recasting nested Born-Oppenheimer hierarchies within this same formalism and benchmarking against modern ab initio potential energy surfaces, we show that adiabatic separation of the light particle from
lattice dynamics is satisfied only in the positive-
muon ($\mu^{+}$) mass limit. In contrast, tunneling for H and D is fundamentally a collective, nonadiabatic process mediated by anharmonic
lattice couplings. Finally, we show that the breakdown of adiabaticity can be anticipated from simple energy estimates involving the ground-state light-particle energy evaluated at a small number of fixed
lattice configurations, providing a practical criterion for assessing the validity of adiabatic tunneling theories in other systems.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Optical Transmission of 2D Material with Quantum Anomalous Hall Effect
Nathan Pravda, Oleg L. Berman and Klaus Ziegler
We study the optical properties of gapped two-dimensional materials which are subject to the
quantum anomalous
Hall effect. At sufficiently low temperatures the transmission, reflection and absorption coefficients are found to have a universal behavior that depends only on the ratio of the photonic energy and the gap energy. There is a singular behavior with total reflection when these energies are equal. In the limit of a vanishing gap we recover results for
graphene, where the optical coefficients depend only on the fine-structure constant. The observed optical properties provide an accurate measurement of the bandgap.
Read the full abstract ▾
Quantum Gases · Cross-listed from hep-ph
Yukawa-Screened Bose-Star Condensation
Jiajun Chen
We study Bose-
star formation in a Yukawa-Schrödinger-Poisson (YSP) system. A finite interaction range suppresses the infrared kinetic relaxation responsible for Bose-
star condensation, modifying both the
equilibrium Bose-
star structure and the condensation timescale. We derive a screened kinetic condensation formula in which the ordinary gravitational Coulomb logarithm is replaced by a finite Yukawa transport logarithm. Static YSP solutions show that Yukawa screening broadens the Bose-
star density profile relative to the ordinary Newtonian
soliton. Fully dynamical pseudospectral simulations with homogeneous and isotropic initial conditions demonstrate that Yukawa screening systematically delays Bose-
star condensation, in good agreement with the screened kinetic prediction after fitting a single overall normalization parameter.
Read the full abstract ▾
Materials Science
Pulsed thermal annealing enables switching of chiral antiferromagnetic order with a sub-millitesla field in Mn$_3$Sn
Xiaokang Li, Jing Zhang, Xiaodong Guo et al. (+1 more)
The manipulation of
antiferromagnetic (AFM) order is a central theme in modern spintronics. In this work, we achieve reliable switching of the
chiral AFM state in the Weyl antiferromagnet Mn$_3$Sn using a heat pulse combined with a very small
magnetic field as small as 0.1 mT. By systematically measuring the anomalous
Hall effect (AHE) in high-quality single
crystals, we show that the field needed for switching decreases as the temperature approaches the Néel temperature $T_N$, and vanishes at $T_N$. Pulsed thermal annealing above $T_N$ followed by cooling in a tiny external field enables full and reproducible switching of the
magnetic octupole order. Our results show that thermal softening (heating above $T_N$ to temporarily remove the
magnetic anisotropy) is a key step that lowers the energy barrier to nearly zero. This allows an extremely weak directional field (like the effective field from
spin-orbit torque in thin-film devices) to set the final
magnetic state during cooling. We also provide a simple model to estimate the temperature rise in nanoscale devices under current pulses, giving practical guidance for device design. This work highlights that thermal effects are not a side issue but an important partner to
spin torques, and suggests that future work should take both into account.
Read the full abstract ▾
All authors Xiaokang Li, Jing Zhang, Xiaodong Guo, Zengwei Zhu
Strongly Correlated Electrons
Tuning J$_1$-J$_2$ in Quasi-2D Triangular Lattice Antiferromagnet $\alpha$-SrCr$_2$O$_4$ via Uniaxial Pressure
Jazzmin Victorin, Shreenanda Ghosh, Seyed Koohpayeh et al. (+2 more)
Triangular
lattice antiferromagnets first attracted
attention as a frustrated
magnetic lattice which can serve as a platform to realize the resonating valence bond state. While the triangular
lattice itself was shown to support classical 120 degree order, many theoretical phase diagrams suggest a
quantum spin liquid state within a small range of parameters. One possible avenue to achieve such a state is to tune the anisotropy of the triangular
lattice antiferromagnet by applying uniaxial pressure. This motivated our Raman scattering study of quasi-two-dimensional antiferromagnet $\alpha$-SrCr$_2$O$_4$ under applied uniaxial pressure. Under ambient conditions, $\alpha$-SrCr$_2$O$_4$ develops long-range helical
magnetic order below T$_N$ = 43 K. We identify two-
magnon excitations associated with this long-range
antiferromagnetic order below T$_N$ at 15.5 meV and 40 meV by comparison with
spin wave calculations. We observe the two features from the two-
magnon excitation shift away from (towards) each other under applied tensile (compressive) pressure, indicating a decrease (increase) in anisotropy. Raman active
phonons show a shift to higher (lower) frequencies under applied compressive (tensile) pressure, indicating efficient transmission of pressure and tuning of the
lattice. We show
spin wave and two-
magnon density of states calculations under uniaxial pressure are consistent with our experimental results.
Read the full abstract ▾
All authors Jazzmin Victorin, Shreenanda Ghosh, Seyed Koohpayeh, Chris Lygouras, Natalia Drichko