Quantum Gases
Polarization-controlled pattern formation in antiparallel dipolar binary condensates
Zhijun Zhang, Weijing Bao, Changjian Yu et al. (+3 more)
We investigate non-
equilibrium pattern formation in an antiparallel two-component dipolar Bose-Einstein condensate by varying the polarization angle and the trap aspect ratio. At finite tilt, the condensate supports stripe order. Quenching the angle to zero triggers a roton-assisted, mushroom-like corrugation that destroys translational order and drives the system into labyrinthine textures, whereas a slow linear ramp produces long-lived curved stripes that ultimately converge to labyrinths. Population imbalance strongly biases the
evolution: the minority component preferentially fragments into a stable droplet array while the majority remains comparatively diffuse; once formed, the droplet
crystal is robust under polarization hysteresis with largely reversible shape changes and unchanged
lattice topology. The trap aspect ratio controls both the initial stripe number and the instability timescale, with tighter axial confinement accelerating corrugation and yielding denser labyrinths at late times. All behaviors arise within a quasi-two-dimensional mean-field regime where beyond-mean-field corrections are negligible; accordingly, the droplets reported here are not self-bound in free space. The observed textures (such as stripes, curved stripes, and labyrinths) mirror the taxonomy and instability pathways of
nuclear "pasta" morphologies (rods and slabs) known from
neutron-
star and
supernova matter, highlighting polarization angle, trap geometry, and population imbalance as practical, experimentally accessible controls for selecting and steering patterns in dipolar mixtures.
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All authors Zhijun Zhang, Weijing Bao, Changjian Yu, Jinbin Li, Gentaro Watanabe, Kui-Tian Xi
Superconductivity
Structural reconstruction as the origin of the cuprate pseudogap
Sophie Beck and Aline Ramires
High-temperature superconductivity in the cuprates emerges from an enigmatic metallic state, known as the pseudogap, characterized by a reconstructed
Fermi surface, reduced carrier density, and the appearance of
Fermi arcs, whose origin remains unresolved. Here, we show that these defining signatures naturally arise from a structural reconstruction observed experimentally that introduces a
symmetry-enforced sublattice degree of freedom. In the presence of
spin-orbit coupling, the
Fermi surface is reconstructed into small closed pockets, effectively reducing the carrier density. The same sublattice structure gives rise to
matrix-element interference in angle-resolved photoemission spectroscopy, leading to the manifestation of
Fermi arcs. Density functional theory calculations support this mechanism. These results demonstrate that
lattice symmetry provides a unifying and experimentally verifiable framework for understanding the pseudogap regime in the cuprates.
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Soft Condensed Matter
Macroscopic active matter under confinement: dynamical heterogeneity, bursts, and glassy behavior in a few-body system of self-propelling camphor surfers
Marco Leoni, Matteo Paoluzzi, Christian Alistair Dumaup et al. (+5 more)
We study a few-body system composed of self-propelling camphor surfers confined within a circular boundary. These millimeter-sized particles move in a regime where inertia and long-ranged interactions play a significant role, leading to surprisingly complex and subtle collective dynamics. These dynamics include self-organized bursts and glassy behavior at intermediate densities–phenomena not apparent from ensemble-averaged steady-state measures. By analyzing quantities like the overlap order parameter, we observe that the system exhibits dynamical slowing down as particle density increases. This slowdown is also reflected in the bursting activity, where both the amplitude and frequency of bursts decrease with increasing particle density. A minimal inertial active-particle model reproduces these dynamical steady states, revealing the importance of a new intermediate length scale–larger than the particle size. This intermediate scale is critical for the formation of structures resembling caging and plays a key role in the glass-like transition. Our results describe a macroscopic analog of an active glass with the additional phenomena of density-dependent bursting.
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All authors Marco Leoni, Matteo Paoluzzi, Christian Alistair Dumaup, Farbod Movagharnemati, Lauren Nguyen-Leon, Tiffany Nguyen, Sarah Eldeen, Wylie W. Ahmed
Materials Science
Mean field magnetism and spin frustration in a double perovskite oxide with compositional complexity
Nandana Bhattacharya, Ravi Kiran Dokala, Sourav Chowdhury et al. (+9 more)
The rise of high-
entropy oxides as a major functional materials design principle in recent years has prompted us to investigate how compositional disorder affects long-range
magnetic ordering in double perovskite
oxides. Since
ferromagnetic insulators are emerging as an important platform for lossless spintronics, we consider the $RE_2$NiMnO$_6$ ($RE$ : rare-earth) family and investigate single-crystalline films of (La$_{0.4}$Nd$_{0.4}$Sm$_{0.4}$Gd$_{0.4}$Y$_{0.4}$)NiMnO$_{6}$ grown on SrTiO$_3$ (001) substrates in this work. Despite configurational disorder and high cationic size variance at the $RE$ site, the material exhibits robust
ferromagnetic ordering with a Curie temperature ($T_\mathrm{c}$) of approximately 150 K. This $T_\mathrm{c}$ is consistent with the expectation based on consideration of the average ionic radii of the rare-earth ($RE$) sites in the bulk $RE_2$NiMnO$_6$. Below $T_\mathrm{c}$, Raman spectroscopy measurement finds a deviation from anharmonic behavior, where the
phonon renormalization aligns with a mean-field approximation of
spin-
spin correlation. At lower temperature,
magnetic $RE$ ions also contributed to the
magnetic behavior and the system displays a reentrant
spin-glass-like behavior. This study demonstrates that while a mean-field approach serves as a viable starting point for predicting the long-range transition temperature, microscopic details of the complex
magnetic interactions are essential for understanding the low-temperature phase.
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All authors Nandana Bhattacharya, Ravi Kiran Dokala, Sourav Chowdhury, Suresh Chandra Joshi, Subha Dey, Jayjit Kumar Dey, Subhajit Nandy, Daniel Perez Salinas, Manuel Valvidares, Moritz Hoesch, Roland Mathieu, Srimanta Middey
Soft Condensed Matter
Adhesive strength of bio-inspired fibrillar arrays in the presence of contact defects
Agostinelli Daniele, Shojaeifard Mohammad and Bacca Mattia
The performance of bio-inspired fibrillar adhesives can be compromised by surface roughness, manufacturing imperfections or
impurities. Previous studies investigated the cases of distributed defects on the array, and defects at the level of single fibrils. However, the influence of localized, macroscopic defects remains largely unexplored. Using numerical simulations of a discrete mechanical model for a fibrillar adhesive with a thick backing layer, we investigate how the size and location of a single circular defect affect the established scaling law between the adhesion force ($F$) and the effective compliance of the system ($\beta$), \ie, $F \propto \beta^{-1/2}$. We find that edge defects are generally more detrimental than central ones, as they act as pre-cracks that amplify stress concentrations at the adhesive's edge, accelerating a crack-like failure. Consequently, the established adhesion scaling law is preserved, with the defect only reducing the effective contact area. In contrast, a central defect fundamentally alters the mechanics of detachment. By transforming the contact geometry into an annulus, it promotes more uniform load sharing across the remaining fibrils and mitigates the edge-dominated failure mechanism. This change makes the adhesive strength less sensitive to the compliance of the system, as reflected by a less negative scaling exponent. The transition between these two regimes appears to occur for defects whose boundary merges with the one of the adhesive. These results provide practical guidance for the design, engineering and quality control of bio-inspired fibrillar adhesives.
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Soft Condensed Matter
Vorticity-induced surfing and trapping in porous media
Pallabi Das, Mirko Residori, Axel Voigt et al. (+2 more)
Microorganisms often encounter strong confinement and complex hydrodynamic flows while navigating their habitats. Combining finite-element methods and
stochastic simulations, we study the interplay of active transport and heterogeneous flows in dense porous channels. We find that swimming always slows down the traversal of
agents across the channel, giving rise to robust power-law tails of their exit-time distributions. These exit-time distributions collapse onto a universal master curve with a scaling exponent of $\approx 3/2$ across a wide range of packing fractions and motility parameters, which can be rationalized by a scaling relation. We further identify a new motility pattern where
agents alternate between surfing along fast streams and extended trapping phases, the latter determining the power-law exponent. Unexpectedly, trapping occurs in the flow backbone itself – not only at obstacle boundaries – due to vorticity-induced reorientation in the highly-heterogeneous fluid environment. These findings provide a fundamentally new active transport mechanism with direct implications for biofilm clogging and the design of novel microrobots capable of operating in heterogeneous media.
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All authors Pallabi Das, Mirko Residori, Axel Voigt, Suvendu Mandal, Christina Kurzthaler
Mesoscale and Nanoscale Physics · Cross-listed from physics.chem-ph
Unlocking n-alk-1-ynes Conformers: Quantum "Trigger Finger" versus "Stiff Joint" Conformations
Ioan Bâldea
Molecular conformation in n-alk-1-ynes (CnA) is conventionally simplified to an all-planar structure. We report a comprehensive
quantum chemical analysis revealing two near-isoenergetic rotamers at the acetylenic terminus: planar (C$_s$) and skewed (C$_1$). The high, symmetric rotational energy barrier ($\approx 150$\,meV) arises from unique steric relief near the $\mathrm{sp}$ center coupled with electronic stabilization of C$_1$. This creates a unique kinetic profile: a
Quantum “Trigger Finger” ($\alpha$ rotation) that enforces an $\approx 50\%:\,50\%$ $\mathrm{C}_s/\mathrm{C}_1$ ensemble, sharply contrasting with the thermodynamically biased “Stiff Joint” ($\delta$ rotation) of the alkyl chain. This structural degeneracy necessitates ensemble averaging for spectroscopic data interpretation, while the slow interconversion permits kinetic trapping and intentional conformer enrichment during synthesis and molecular junction fabrication. Our work redefines the alkyne anchor, providing a blueprint for accurate interpretation of spectroscopic data and achieving conformational control in molecular electronics.
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Superconductivity
Theoretical analysis of photon detection mechanism in superconducting single-photon detectors
Yusuke Masaki and Hiroaki Matsueda
To elucidate the
photon detection mechanism of superconducting single-
photon detectors, we theoretically examine the dynamics of type-II
superconductors with a bias current using the two-dimensional time-dependent Ginzburg-Landau and the Maxwell equations. The
photon injection that weakens the superconducting order parameter is treated phenomenologically as a local temperature increase, and the amount of injection is controlled by the initial hotspot radius. The
photon is detected by the voltage change between two electrodes attached to the left and right edges of the
superconductor. We find that certain parameter ranges can be explained by the traditionally considered hotspot model, while other parameter ranges are governed by the generation and annihilation of superconducting
vortex and antivortex pairs. The
photon detection is possible for an initial hotspot radius that exceeds a threshold value. We find that the generation of a
vortex–antivortex pair occurs near the threshold. The flow of the pair perpendicular to the current direction finally creates a normal region for the
photon detection. The voltage change for the Ginzburg–Landau parameter close to the transition point from type-II to type-I
superconductor shows anomalous behavior that is not associated with the dynamics of the
vortex–antivortex pair. We also examine the effects of spatially non-uniform current density on the voltage change and the superconducting order parameter to provide a hint to understand the behavior of wide-strip single-
photon detectors. The estimated values of incident
photon energy and response time for
photon detection are reasonable in comparison with experiments. The present comprehensive examination provides useful guidelines for flexible design of device structures.
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Other Condensed Matter
Deterministic generation of single B centers in hBN by one-to-one conversion from UV centers
Andrés Núñez Marcos, Christophe Arnold, Julien Barjon et al. (+3 more)
Among the variety of
quantum emitters in hexagonal boron nitride (hBN), blue-emitting color centers, or B centers, have gathered a particular interest owing to their excellent
quantum optical properties. Moreover, the fact that they can be locally activated by an electron beam makes them suitable for top-down integration in photonic devices. However, in the absence of a real-time monitoring technique sensitive to individual emitters, the activation process is
stochastic in the number of emitters, and its mechanism is under debate. Here, we implement an in-situ cathodoluminescence monitoring setup capable of detecting individual
quantum emitters in the blue and ultraviolet (UV) range. We demonstrate that the activation of individual B centers is spatially and temporally correlated with the deactivation of individual UV centers emitting at 4.1 eV, which are ubiquitous in hBN. We then make use of the ability to detect individual B center activation events to demonstrate the controlled creation of an array with only one emitter per irradiation site. Additionally, we demonstrate a symmetric technique for heralded selective deactivation of individual emitters. Our results provide insights into the microscopic structure and activation mechanism of B centers, as well as versatile techniques for their deterministic integration.
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All authors Andrés Núñez Marcos, Christophe Arnold, Julien Barjon, Stéphanie Buil, Jean-Pierre Hermier, Aymeric Delteil
Soft Condensed Matter
Granular drag and lift force on a flexible fiber
Antonio Pol, Sara Storti and Fabio Gabrieli
In this work, we investigate the forces acting on a flexible fiber dragged through a granular bed. Using discrete element simulations, we observe that, after a sufficiently large displacement, the system reaches a steady state in which both the fiber's shape and the forces acting on it become, on average, constant. Under these conditions, we identify two characteristic lengths that describe the fiber's shape and propose unique scaling laws for the drag and lift forces, valid across a wide range of fiber flexibilities, from highly deformable to nearly rigid, based on these lengths. We highlight that the fiber-grains interaction is governed by a single dimensionless elastogranular parameter, defined as the ratio of the fiber's elastic properties to the granular pressure. Finally, we demonstrate that both the forces and the characteristic lengths can be expressed solely as functions of this dimensionless parameter. Our findings offer a fundamental insight into the behavior of a flexible fiber interacting with a granular medium.
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Materials Science
Ultrafast magnetic moment transfer and bandgap renormalization in monolayer FeCl$_2$
Yu-Hui Song, Huan-Cheng Yang, Kai Liu et al. (+1 more)
The microscopic origin of
laser-induced ultrafast demagnetization remains an open question, to which the non-thermal electronic distribution plays a vital role at the initial stage. Herein, we investigate the connection between the non-thermal electronic distribution and the ultrafast
spin dynamics as well as the electronic structure
evolution in
ferromagnetic FeCl$_2$ monolayer using real-time time-dependent density functional theory (rt-TDDFT) with self-consistent Hubbard $U$ correction. Our simulations reveal that femtosecond
laser pulses induce ultrafast
magnetic moment transfer from Fe to Cl atoms. More importantly, through a comprehensive analysis of orbital-resolved electronic structure, we elucidate the microscopic origin of this transfer, attributing it to specific intra-atomic and inter-atomic charge transfer pathways driven by non-thermal excitations. The extent of demagnetization of Fe atoms exhibits a non-monotonic dependence on the
laser photon energy, reaching a maximum at the resonant excitation. In addition, the dynamical
evolution of the band structure was studied based on the eigenstates of the instantaneous
Hamiltonian. Under resonant excitation, the bandgap reduction reaches up to $41\%$ within tens of fs. These findings provide fundamental insights into ultrafast
spin control and suggest a strategy to optically engineer the magnetism in two-dimensional
magnetic materials.
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All authors Yu-Hui Song, Huan-Cheng Yang, Kai Liu, Zhong-Yi Lu
Superconductivity
Spin and orbital excitations in undoped infinite layers: a comparison between superconducting PrNiO2 and insulating CaCuO2
Francesco Rosa, Hoshang Sahib, Giacomo Merzoni et al. (+9 more)
Infinite-layer nickelates are among the most promising cuprate-akin
superconductors, although relevant differences from copper
oxides have been reported. Here, we present momentum- and polarization-resolved RIXS measurements on chemically undoped, superconducting PrNiO2, and compare its
magnetic and orbital excitations with those of the reference infinite layer cuprate CaCuO2. In PrNiO2, the in-plane
magnetic exchange integrals are smaller than in CaCuO2, whereas the out-of-plane values are similar, indicating that both materials support a three-dimensional
antiferromagnetic order. Orbital excitations, associated to the transitions within 3d states of the metal, are well reproduced within a single-ion model and display similar characteristics, except for the Ni-dxy peak which, besides lying at significantly lower energy, shows an opposite dispersion to that of Cu-dxy. This is interpreted as a consequence of orbital superexchange coupling between nearest neighbor sites, which drives the orbiton propagation. Our observations demonstrate that infinite layer cuprates and nickelates share most of the
spin and orbital properties, despite their markedly different charge-transfer energy Delta.
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All authors Francesco Rosa, Hoshang Sahib, Giacomo Merzoni, Leonardo Martinelli, Riccardo Arpaia, Nicholas B. Brookes, Daniele Di Castro, Krzysztof Wohlfeld, Maryia Zinouyeva, Marco Salluzzo, Daniele Preziosi, Giacomo Ghiringhelli
Materials Science
Non-altermagnetic spin texture in MnTe
Meng Zeng, Pengfei Liu, Ming-Yuan Zhu et al. (+19 more)
Recently, altermagnets have emerged as promising candidates in spintronics, uniquely combining large
spin-polarized electronic states with zero net magnetization. A prominent example is $\alpha$-MnTe, whose altermagnetic
spin splitting, i.e., the degeneracy lift in momentum space induced by collinear
magnetic order, has been experimentally observed. However, the direct evidence of its $g$-wave
spin polarization, the key property for altermagnetic spintronics, is thus far lacking. By combining high-resolution
spin- and angle-resolved photoemission spectroscopy (SARPES) with first-principles calculations, we reveal a $k_z$-independent, Rashba-like
spin texture in $\alpha$-MnTe. Our results indicate that the observed
spin polarization is primarily governed by
spin-orbit coupling, whereas the
magnetic order contributes to the splitting of energy bands but plays a much less dominant role in
spin polarization due to the multi-domain nature. From this result, we further establish a way to prescreen altermagnet candidates that favor the formation of large
antiferromagnetic domains based on
symmetry analysis. Our work elucidates the interplay between
magnetic order and
spin-orbit coupling in governing
spin polarization in altermagnet candidates, and thereby advances the materials design paradigm for
spin-functional devices.
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All authors Meng Zeng, Pengfei Liu, Ming-Yuan Zhu, Naifu Zheng, Xiang-Rui Liu, Yu-Peng Zhu, Tian-Hao Shao, Yu-Jie Hao, Xiao-Ming Ma, Gexing Qu, Rafał Kurleto, Dawid Wutke, Rong-Hao Luo, Yue Dai, Xiaoqian Zhang, Koji Miyamoto, Kenya Shimada, Taichi Okuda, Kiyohisa Tanaka, Yaobo Huang, Qihang Liu, Chang Liu
Materials Science
Parity Anomalous Semimetal with Minimal Conductivity Induced by an In-Plane Magnetic Field
Binbin Wang, Jiayuan Hu, Bo Fu et al. (+5 more)
The interplay between topological materials and local
symmetry breaking gives rise to diverse topological
quantum phenomena. A notable example is the parity anomalous semimetal (PAS), which hosts a single unpaired gapless Dirac cone with a half-integer quantized
Hall conductivity. Here, we realize this phase in a
magnetic topological sandwich structure by applying an in-plane
magnetic field. This configuration aligns the magnetization of one surface in-plane while preserving magnetization out-of-plane on the opposite surface, satisfying the condition for a gapless surface state near the
Fermi level on only one surface. Our key evidence is a distinctive two-stage
evolution of the conductivity tensor ($\sigma_{xy}$, $\sigma_{xx}$). The first stage culminates in the PAS at the fixed point ($\frac{e^2}{2h}$, $m \frac{e^2}{h}$), where $m \approx 0.6$ corresponds to the minimal longitudinal conductivity of a single gapless Dirac cone of
fermions on a 2D
lattice. This PAS state remains stabilized and is superposed with a gapped band flow in the second stage. This observation demonstrates that this state stabilized by the in-plane field resists localization–contrary to conventional expectations for 2D electron systems with broken time reversal
symmetry. The dynamic transition from an integer quantized
insulator to a half-integer quantized semimetal establishes this material system as a versatile platform for exploring parity anomaly physics.
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All authors Binbin Wang, Jiayuan Hu, Bo Fu, Jiaqi Li, Yunchuan Kong, Kai-Zhi Bai, Shun-Qing Shen, Di Xiao
Disordered Systems and Neural Networks
On the supra-linear storage in dense networks of grid and place cells
Adriano Barra, Martino S. Centonze, Michela Marra Solazzo et al. (+1 more)
Place-
cell networks, typically forced to pairwise synaptic interactions, are widely studied as models of cognitive maps: such models, however, share a severely limited storage capacity, scaling linearly with network size and with a very small critical storage. This limitation is a challenge for
navigation in 3-dimensional space because, oversimplifying, if encoding motion along a one-dimensional trajectory embedded in 2-dimensions requires $O(K)$ patterns (interpreted as bins), extending this to a 2-dimensional
manifold embedded in a 3-dimensional space – yet preserving the same resolution – requires roughly $O(K^2)$ patterns, namely a supra-linear amount of patterns. In these regards, dense Hebbian architectures, where higher-order neural assemblies mediate
memory retrieval, display much larger capacities and are increasingly recognized as biologically plausible, but have never linked to place
cells so far. Here we propose a minimal two-layer model, with place
cells building a layer and leaving the other layer populated by neural units that account for the internal representations (so to qualitatively resemble grid
cells in the MEC of mammals): crucially, by assuming that each place
cell interacts with pairs of grid
cells, we show how such a model is formally equivalent to a dense Battaglia-Treves-like Hebbian network of grid
cells only endowed with four-body interactions. By studying its emergent computational properties by means of statistical mechanics of disordered systems, we prove – analytically – that such effective higher-order assemblies (constructed under the guise of biological plausibility) can support supra-linear storage of continuous attractors; furthermore, we prove – numerically – that the present neural network is capable of recognition and
navigation on general surfaces embedded in a 3-dimensional space.
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All authors Adriano Barra, Martino S. Centonze, Michela Marra Solazzo, Daniele Tantari
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Demonstration of on-chip all-optical switching of magnetization in integrated photonics
Pingzhi Li, Gijs W.A. Simons, Tianyu Zhang et al. (+7 more)
Ultrafast all-optical magnetization switching (AOS) holds great promise for nextgeneration spintronic
memory and hybrid spintronic-photonic systems. However, most implementations to date rely on bulky free-space optical setups, limiting scalability and practical integration. As a critical step toward integrated applications, we demonstrate single-pulse AOS within a silicon nitride (Si3N4) photonic integrated
circuit. Using trains of femtosecond
laser pulses guided through on-chip waveguides, we achieve deterministic toggle switching in a sub-micron out-of-plane Co/Gd
Hall cross patterned directly atop the photonic waveguide. Electrical readout via the anomalous
Hall effect reveals a switching contrast of up to 90% for 500 nm-wide devices. In larger
Hall crosses, the contrast decreases and switching becomes
stochastic, consistent with spatially non-uniform optical absorption as confirmed by finite-element simulations. This behavior is hypothetically attributed to domain wall relaxation and thermally assisted (de)pinning processes within partially switched regions. Our results highlight the critical role of device scaling in achieving robust on-chip AOS and establish a foundation for ultrafast, energy-efficient, and fully integrated spintronic-photonic platforms.
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All authors Pingzhi Li, Gijs W.A. Simons, Tianyu Zhang, Philip P.J. Schrinner, Sohrab Kamyar, Ronald Dekker, Diana C. Leitao, Reinoud Lavrijsen, Yuqing Jiao, Bert Koopmans
Quantum Gases
The bulk modulus of three-dimensional quantum droplets
Zibin Zhao, Guilong Li, Zhaopin Chen et al. (+4 more)
Quantum droplets (QDs), formed by ultradilute
quantum fluids under the action of the Lee-Huang-Yang (LHY) effect, provide a unique platform for investigating a wide range of macroscopic
quantum effects. Recent studies of QDs' breathing modes and collisional dynamics have revealed their compressibility and extensibility, which suggests that their elasticity parameters can be identified. In this work we derive the elastic bulk modulus (BM) of QDs by means of theoretical analysis and numerical simulations and establish a relation between the BM and the eigenfrequency of the QD's intrinsic vibrations. The analysis reveals the dependence of the QD's elasticity on the particle number and the strength of interparticle interactions. We additionally provide a realistic estimate of the bulk modulus for the system, yielding a concrete physical value that may serve as a reference for future experimental measurements. Taken together, these results also point to possibilities for realizing elastic media governed by the LHY effect.
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All authors Zibin Zhao, Guilong Li, Zhaopin Chen, Huan-Bo Luo, Bin Liu, Boris A. Malomed, Yongyao Li
Mesoscale and Nanoscale Physics
Acoustic orbital Hall effect and orbital pumping in light-metal-ferromagnet bilayers
Mingxing Wu, Shilei Ding, Hiroki Matsumoto et al. (+1 more)
Orbital currents provide a new degree of freedom for controlling magnetism, yet their interaction with
lattice dynamics remains largely unexplored. Here we report a systematic investigation of the acoustic orbital
Hall effect in light metals such as Ti and Cr, where surface acoustic waves generate orbital currents through
phonon-orbital coupling. The acoustic orbital current in Ti exhibits higher efficiency and longer
diffusion length compared to the acoustic
spin current in Pt. The sign and magnitude of the rectified acoustic voltages in nonmagnetic (Ti, Cr)/
ferromagnetic (Ni, Co, Fe$_x$Co$_{1-x}$)
bilayers are determined by the product of orbital-to-
spin conversion and magnetoelastic coupling efficiencies of the ferromagnet. Additionally, we find evidence for acoustic orbital pumping, whereby the excitation of
ferromagnetic resonance by surface acoustic waves injects an orbital current from the ferromagnet into the nonmagnet. These results establish
lattice dynamics as an efficient driver of orbital transport, opening opportunities for low-dissipation orbitronic devices that harness and sense
phonons.
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All authors Mingxing Wu, Shilei Ding, Hiroki Matsumoto, Pietro Gambardella
Materials Science
Strain-Tunable Opto-electronics in PdS$_2$ Monolayer: the Role of Band Nesting and Carrier-Phonon Scattering
Hongfa Wang, Yancheng Gong, Subrahmanyam Pattamatta et al. (+3 more)
Strain engineering is a powerful strategy for tuning the optoelectronic properties in two-dimensional materials, yet the underlying mechanisms governing their strain response are often not fully elucidated. In this work, our first-principle calculations show that the penta-orthorhombic PdS$_2$ monolayer exhibits two key strain-tunable properties: a continuous
redshift of its main optical absorption peak from $\sim$2.0 to $\sim$1.6~eV and enhancement in carrier mobility, with a more than threefold increase for electron under 0–4% biaxial tensile strain. Subsequent analysis reveals that the tunable optical response originates from a robust band nesting feature between the highest valence and lowest conduction bands, which is preserved across the Brillouin zone under biaxial strain. For the carrier transport, deformation potential theory predicts mobility increasing with strain, strongly correlating with the reduction of carrier effective mass. Our first-principles calculations show a strain-induced monotonic decrease in carrier linewidths near the band edges, indicating suppressed carrier-
phonon scattering and longer carrier lifetime as the origin of the mobility enhancement. Our work establishes a pathway for engineering the optoelectronic response in 2D
semiconductors where strong band nesting governs the optical properties and paves the way for the rational design of continuously tunable flexible optoelectronic devices.
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All authors Hongfa Wang, Yancheng Gong, Subrahmanyam Pattamatta, Junwen Li, Hailong Wang, Zhizi Guan
Statistical Mechanics
Charge glass from supercooling topological-ordered liquid
Kouki Kimata, Harukuni Ikeda and Masafumi Udagawa
Topological order characterizes a class of
quantum and classical many-body
liquid states that escape the conventional classification by spontaneous
symmetry breaking. Many properties of the topological-ordered states still await a clear understanding, and nature of phase transition dynamics is one of them. Normally, when a
liquid freezes into a solid, crystallization starts with nucleation and a solid domain quickly grows on the surface of the expanding
nucleus, and the domains evolve into macroscopic size. In this work, we reveal that the crystallization of the topological-ordered
liquid proceeds in a fundamentally different way. The topological-ordered phase is characterized by a global conserved quantity and its conjugate fractional charge, which we call a flux and a triplet in our working system of the charge Ising model on a triangular
lattice. In contrast to the normal crystallization process, the phase transition is driven by the diffusive motion of triplets, which is required to change the value of conserved fluxes to exit the topological-ordered phase. In order to complete crystallization, triplets must spend a divergently long time to diffuse over a macroscopic distance across the system, which results in glassy behavior. Reflecting the diffusive motion of triplets, the initial crystallization process shows slowing down with unusually small Avrami exponent $\sim0.5$. These anomalous dynamics are specific to the crystallization from topological-ordered
liquid, and well account for the main features of charge glass behavior exhibited by the organic conductors, $\theta$-(BEDT-TTF)$_2$X(SCN)$_4$.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Decay of transmon qubit in a broadband one-dimensional cavity
Ya. S. Greenberg, A. A. Shtygashev and O. V. Kibis
We investigate the decay dynamics of a three-level artificial atom, a superconducting transmon
qubit, weakly coupled to a continuum of modes in a broadband, one-dimensional cavity. Using the resolvent formalism, we derive analytical expressions for the resonance frequency shifts and widths, which are then evaluated numerically for a Gaussian density of states. We identify two distinct dynamical regimes, differentiated by the ratio of the
qubit's coupling strength to the continuum bandwidth. When this ratio is much less than one, the system exhibits a Markovian regime in which the resonance width is practically independent of energy within the continuum band. As the ratio increases, the system transitions to a non-Markovian regime where the resonance width becomes strongly energy-dependent. In this regime, the
qubit interacts with the continuum faster than the continuum can erase the information from the
qubit's past. Furthermore, we demonstrate that the coupling between the transmon's second level and its ground state significantly influences the decay dynamics of the third level. The interaction between these two levels opens a fast two-
photon decay channel, which broadens the transmon's second level.
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Quantum Gases
Multi-Particle Quantum Walks in a Dipole-Conserving Bose-Hubbard Model
Sooshin Kim, Byungmin Kang, Perrin Segura et al. (+4 more)
When particles move through a
crystal or optical
lattice, their motion can sometimes become frozen by strong external forces – yet collective motion may still emerge through subtle many-body effects. In this work, we explore such constrained dynamics by realizing a dipole-conserving Bose-Hubbard model, where single atoms are immobile but pairs of particles can move cooperatively while preserving the system's center of mass, i.e. the overall dipole moment of the particle distribution. Starting from a one-dimensional chain of ultracold bosonic atoms in an optical
lattice, we generate localized dipole excitations consisting of a hole and a doublon using site-resolved optical potentials and characterize their
quantum walks and scattering dynamics. Our study provides a bottom-up investigation of a
Hamiltonian with kinetic constraints, and paves the way for exploring low-energy phases of fractonic matter in existing experimental platforms.
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All authors Sooshin Kim, Byungmin Kang, Perrin Segura, Yanfei Li, Ethan Lake, Brice Bakkali-Hassani, Markus Greiner
Mesoscale and Nanoscale Physics · Cross-listed from physics.app-ph
Monochromatic Electron Emission from Graphene-Insulator-Semiconductor-Structured Electron Source Utilizing Interference Efficets
Takao Koichi, Shogo Kawashima, Hiroshi Miyake et al. (+4 more)
The
graphene-
insulator-
semiconductor-structured electron source has garnered significant
attention due to its high electron emission efficiency and highly monochromatic electron emission.
Graphene, with its c-axis orientation and well-defined interlayer spacing, exhibits electron interference effects that can influence the properties of emitted electrons. In this work, motion of an electron wave packet is numerically calculated to discuss the energy spread of the zero-order and first-order diffracted electron waves by mono- and multilayer
graphene. It is found that the effects of multiple reflections of electron between the layers broaden the energy spread especially for the incident energy of 13.4 eV, and that highly monochromatic electron emission can be achieved by using diffracted electron wave with a small aperture.
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All authors Takao Koichi, Shogo Kawashima, Hiroshi Miyake, Satoshi Abo, Fujio Wakaya, Masayoshi Nagao, Katsuhisa Murakami
Materials Science
$C_{3}$-Symmetry-induced Antisymmetric Planar Hall effect and Magnetoresistance in Single-Crystalline Ferromagnets
W. J. Qin, B. Yang, Y. Z. Tian et al. (+7 more)
The planar
Hall effect (PHE) is typically symmetric under
magnetic field reversal, as required by the Onsager reciprocity relations. Recent advances have identified the antisymmetric PHE (under
magnetic field reversal) as an intriguing extension in
magnetic systems. While new mechanisms have been proposed, the role of conventional anisotropic magnetoresistance (AMR) in this phenomenon remains unclear. Here, we report the experimental discovery of an antisymmetric (with respect to both
magnetic field and magnetization) PHE and magnetoresistance in single-
crystal $Co_{30}Pt_{70}$ (111) thin films with $C_{3}$ rotational
symmetry and perpendicular
magnetic anisotropy (PMA). We demonstrate that both antisymmetric effects arise naturally from the intrinsic fourth-rank AMR tensor inherent to C3-symmetric planes, assisted by PMA. Our findings link conventional AMR to antisymmetric galvanomagnetic responses, offering new insights into
symmetry-governed transport in crystalline ferromagnets.
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All authors W. J. Qin, B. Yang, Y. Z. Tian, B. W. Zheng, K. Y. Wang, B. Y. Huang, Y. B. Yang, W. Q. Zou, D. Wu, P. Wang
Materials Science
Pressure-Driven Phase Evolution and Optoelectronic Properties of Lead-free Halide Perovskite Rb$_2$TeBr$_6$
Suvashree Mukherjee, Asish Kumar Mishra, K.A. Irshad et al. (+2 more)
The structural, vibrational, and optical properties of Rb$_2$TeBr$_6$ have been investigated under high pressure using synchrotron X-ray diffraction, Raman spectroscopy, photoluminescence (PL), and optical absorption measurements. At ambient conditions, Rb$_2$TeBr$_6$ crystallizes in the cubic Fm-3m structure, which remains stable below 8.0 GPa. Within this pressure range, subtle inter-octahedral rotations develop, producing a gradual localized deviation from the ideal cubic framework. This local reorientation facilitates radiative recombination, leading to a pronounced enhancement of PL intensity with pressure up to 2.4 GPa. Beyond this pressure point, enhancement of nonradiative relaxation channels result in gradual PL quenching. Additionally, the PL intensity increases upon the application of an external weak
magnetic field. A structural transition to the orthorhombic Pnnm phase occurs at around 8.0 GPa, followed by a monoclinic P$2_1/m$ phase above 10.7 GPa, and eventual amorphization beyond 25.5 GPa. Optical absorption spectra reveal continuous band-gap narrowing upon compression. These findings demonstrate the strong coupling among
lattice dynamics, electronic structure, and optical response in Rb$_2$TeBr$_6$, underscoring its potential as a pressure-tunable optoelectronic material
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All authors Suvashree Mukherjee, Asish Kumar Mishra, K.A. Irshad, Boby Joseph, Goutam Dev Mukherjee
Superconductivity
Electronic state of superconductivity in line nodal material CaSb2 under pressure up to 4.2 GPa
Shumpei Oguchi, Kenji Ishida, Atsutoshi Ikeda et al. (+2 more)
We report the results of resistance measurements under pressure up to $4.2\,\mathrm{GPa}$ on single-crystalline $\mathrm{CaSb}_2$ , which shows the maximum of superconducting transition temperature $T_\mathrm{c}$ at $3.1\,\mathrm{GPa}$. At room temperature, $R(P)$ shows a subtle anomaly at $3.1\,\mathrm{GPa}$. However, Bloch-Grüneisen analysis of $R(T)$ indicates that the electronic state does not change significantly across $3.1\,\mathrm{GPa}$.
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All authors Shumpei Oguchi, Kenji Ishida, Atsutoshi Ikeda, Yoshiteru Maeno, Shunsaku Kitagawa
Strongly Correlated Electrons
Benchmarking Non-perturbative Many-Body Approaches in the Exactly Solvable Hatsugai-Kohmoto Model
Hui Li, Ziyu Li and Chen-run Yu
The accurate simulation of strongly correlated electron systems remains a central challenge in condensed matter physics, motivating the development of various non-perturbative many-body methods. Such methods are typically benchmarked against the numerical exact determinant
quantum Monte Carlo (DQMC) in the Hubbard model; however, DQMC is limited by the fermionic sign problem and the uncertainties of numerical analytic continuation. To address these issues, we use the exactly solvable Hatsugai-Kohmoto (HK) model as a benchmarking platform to evaluate three many-body approximations: $GW$, $HGW$, and $SGW$. We compare the Green's functions, spectral functions, and response functions obtained from these approximations with the exact solutions. Our analysis shows that the $GW$ approximation, often considered insufficient for describing strong correlation, exhibits a previously unreported solution branch that accurately reproduces Mott physics in the HK model. In addition, using a covariant formalism, we find that $HGW$ provides an accurate description of charge response, while $SGW$ performs well for
spin correlations. Overall, our work demonstrates that the HK model can effectively
benchmark many-body approximations and helps refine the understanding of $GW$ methods in strongly correlated regimes.
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Materials Science
From data to design: Random forest regression model for predicting mechanical properties of alloy steel
Samjukta Sinha and Prabhat Das
This study investigates the application of Random Forest Regression for predicting mechanical properties of
alloy steel-Elongation, Tensile Strength, and Yield Strength-from material composition features including Iron (Fe), Chromium (Cr), Nickel (Ni), Manganese (Mn), Silicon (Si), Copper (Cu), Carbon (C), and deformation percentage during cold rolling. Utilizing a
dataset comprising these features, we trained and evaluated the Random Forest model, achieving high predictive performance as evidenced by R2 scores and Mean Squared Errors (MSE). The results demonstrate the model's efficacy in providing accurate predictions, which is validated through various performance metrics including residual plots and learning curves. The findings underscore the potential of ensemble learning techniques in enhancing material property predictions, with implications for industrial applications in material science.
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Materials Science
Hybridization Gap and Edge States in Strained-layer InAs/In0.5Ga0.5Sb Quantum Spin Hall Insulator
Wenfeng Zhang, Peizhe Jia, Wen-kai Lou et al. (+4 more)
The hybridization gap in strained-layer InAs/InxGa1-xSb
quantum spin Hall insulators (QSHIs) is significantly enhanced compared to binary InAs/GaSb QSHI structures, where the typical indium composition, x, ranges between 0.2 and 0.4. This enhancement
prompts a critical question: to what extent can
quantum wells (QWs) be strained while still preserving the fundamental QSHI phase? In this study, we demonstrate the controlled molecular beam epitaxial (MBE) growth of highly strained-layer QWs with an indium composition of x = 0.5. These structures possess a substantial compressive strain within the In0.5Ga0.5Sb QW. Detailed
crystal structure analyses confirm the exceptional quality of the resulting epitaxial films, indicating coherent
lattice structures and the absence of visible dislocations. Transport measurements further reveal that the QSHI phase in InAs/In0.5Ga0.5Sb QWs is robust and protected by time-reversal
symmetry. Notably, the edge states in these systems exhibit
giant magnetoresistance when subjected to a modest perpendicular
magnetic field. This behavior is in agreement with the Z2 topological property predicted by the Bernevig-Hughes-Zhang (BHZ) model, confirming the preservation of topologically protected edge transport in the presence of enhanced bulk strain.
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All authors Wenfeng Zhang, Peizhe Jia, Wen-kai Lou, Xinghao Wang, Shaokui Su, Kai Chang, Rui-Rui Du
Statistical Mechanics
Schrödinger-invariance in phase-ordering kinetics
Stoimen Stoimenov and Malte Henkel
The generic shape of the single-time and two-time correlators in non-
equilibrium phase-ordering kinetics with ${z}=2$ is obtained from the co-variance of the four-point response functions. Their non-
equilibrium scaling forms follow from a new non-
equilibrium representation of the Schrödinger
algebra.
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