Strongly Correlated Electrons
Particle Dynamics in Constant Synthetic Non-Abelian Fields
Subramanya Bhat K. N., Amita Das, V Ravishankar et al. (+1 more)
Yang-Mills theory has extended well beyond its original role in describing the strong force and now emerges as an effective theory in condensed matter, ultracold atomic, and photonic systems. In these systems, the theory has been successful in explaining phenomena such as the
spin-
Hall effect,
spin transport, and controlling the polarisation of light. Moreover, the ability to engineer and control synthetic non-Abelian gauge fields in these systems enables us to explore aspects of gauge dynamics inaccessible to high-energy experiments. In all the above mentioned cases, the state of the system evolves in an effective external Yang-Mills field. Thus, the study of test particle dynamics in such background fields is interesting in both the classical and
quantum mechanical regimes. The background non-Abelian (color) gauge fields considered in this study are constant, and they generate uniform color
magnetic fields or combined color electric and
magnetic fields – which are relevant configurations. Despite the apparent simplicity of these backgrounds, the coupled
evolution of real space motion and internal color degrees of freedom results in rich, nontrivial behaviour that is qualitatively distinct from the electrodynamic (Abelian) case, such as unbounded trajectories in a constant color
magnetic field. In particular, particle trajectories encode signatures of the underlying gauge sources. Finally, the classical dynamics presented in this paper serves as a precursor to the complete
quantum mechanical treatment to follow.
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All authors Subramanya Bhat K. N., Amita Das, V Ravishankar, Bhooshan Paradkar
Disordered Systems and Neural Networks
Localization and Flat Bands in Bond-Inflated Lattices
Richard Berkovits
We study localization and flat-band formation in
lattices generated by repeated bond inflation of square, honeycomb, and triangular parent
lattices. Replacing each bond by a finite tight-binding chain produces several distinct classes of flat bands: chain-induced flat bands at the eigenenergies of the inserted chains,
symmetry-protected zero-energy flat bands in bipartite bond-inflated
lattices, and nearly flat junction bands near the spectral edges for sufficiently long chains. We analyze these mechanisms for ordered Lieb-$L$, super$^{L}$honeycomb, and super$^{L}$triangular
lattices, and examine their response to bond disorder, site disorder, random
magnetic flux, and randomness in the inflation process itself. While bond and site disorder broaden most flat bands, the zero-energy
chiral band and the junction-induced flat bands remain robust under certain perturbations. Remarkably, substantial flat-band features also persist in randomly bond-inflated graphs, even in the absence of translational
symmetry. In particular, the number of zero-energy states is found to be well estimated by the matching deficiency $N-2\nu(G)$, indicating that local tree-like structure continues to control the low-energy nullity. These results identify bond-inflated
lattices as a broad class of systems in which geometry alone generates robust localization in both ordered and random settings.
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Strongly Correlated Electrons
Unconventional entanglement scaling and quantum criticality in the long-range spin-one Heisenberg chain with single-ion anisotropy
Patrick Adelhardt, Sean R. Muleady, Kai P. Schmidt et al. (+1 more)
Long-range interactions can fundamentally reshape the low-energy properties of low-dimensional
quantum matter, altering both continuous
symmetry breaking and topological phenomena. However, their impact on the
quantum criticality separating these regimes remains poorly understood. We determine the ground-state phase diagram and critical properties of the
spin-one Heisenberg chain with single-ion anisotropy and staggered
antiferromagnetic power-law interactions, using
matrix-product state (MPS) calculations complemented by high-order series expansions (pCUT+MC). Such long-range, non-frustrated interactions circumvent the Hohenberg-Mermin-Wagner
theorem, thereby stabilizing continuous
symmetry breaking (CSB) phases in direct competition with the Haldane phase. We map out the resulting phase diagram and analyze the
entanglement entropy scaling behavior in the U(1) and SU(2) CSB phases, finding logarithmic corrections beyond the short-range, universal contributions expected from linearly dispersed Goldstone modes. We further characterize all critical boundaries through finite-size scaling of either the
entanglement entropy or the staggered magnetization. In particular, the large-D-to-U(1)-CSB transition exhibits unconventional, continuously varying critical exponents as a function of the long-range decay exponent with a strong dependence on the imposed boundary conditions leading to distinct finite-size scalings for sufficiently long-range potentials. Remarkably, the Haldane-to-U(1)-CSB transition likewise displays unconventional
quantum criticality with distinct continuously varying critical exponents. Our work positions this model as a target for near-term atomic platforms with tunable long-range couplings and exhibiting natural single-ion anisotropy, offering a minimal playground for exploring the interplay between long-range interactions, continuous
symmetry breaking, and
topology.
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All authors Patrick Adelhardt, Sean R. Muleady, Kai P. Schmidt, Alexey V. Gorshkov
Superconductivity
Josephson coupling through a magnetic racetrack
A. A. Mazanik and F. S. Bergeret
We investigate the Josephson coupling between two superconducting electrodes connected by a
ferromagnetic racetrack hosting a Bloch-like domain wall (DW). We show that the interplay between superconductivity and the DW leads to highly non-trivial spatial distributions of the supercurrent, including the formation of current loops and a strong sensitivity to the DW position and orientation. We further demonstrate that the Josephson critical current $I_c$ can be efficiently controlled by the DW position along the racetrack, exhibiting pronounced variations and tunable $0$–$\pi$ transitions. These results provide clear design principles for superconducting racetrack devices and establish domain walls as a viable control element for readout schemes in racetrack
memory architectures.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Decoherence Resilience of the Non-Hermitian Skin Effect
Kunkun Wang, Lei Xiao, Stefano Longhi et al. (+1 more)
Decoherence and dissipation, arising from unavoidable interactions with the environment, can exert a dual influence on transport in physical systems, suppressing coherent propagation while inducing
diffusion and mitigating localization in disordered systems. Non-Hermitian physics reveals a qualitatively different scenario, in which structured dissipation can induce directional bulk-to-boundary transport, known as the non-Hermitian skin effect (NHSE), that remains robust against disorder. Whether such transport can persist, be enhanced or hindered under decoherence, remains a largely open question. Here we experimentally address this question using photonic
quantum walks with two tunable prototypical decoherence channels, dephasing and amplitude damping. Under dephasing, the NHSE survives up to the fully incoherent regime and is observed to even be enhanced by dephasing, yielding drift velocities that exceed those of coherent dynamics. By contrast, amplitude damping shows a pronounced order dependence: applied before the non-Hermitian loss operator, it suppresses and ultimately eliminates the NHSE in the fully incoherent limit; applied afterward, the NHSE persists and can be enhanced at sufficiently large loss strengths. Our work bridges
quantum and classical non-Hermitian dynamics, demonstrates the resilience of the NHSE to decoherence, and opens avenues for harnessing decoherence to enhance directional transport in noisy, nonequilibrium systems.
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All authors Kunkun Wang, Lei Xiao, Stefano Longhi, Peng Xue
Materials Science
Two-Dimensional Ferromagnetism in Monolayers of MnSi
Yuan Fang, Yang Liu, Dmitry V. Averyanov et al. (+6 more)
2D ferromagnets offer valuable insights into the fundamentals of magnetism and stimulate the progress of ultracompact spintronics. The demand for seamless integration of the materials with the Si technology, particularly helpful to their applications in nanoelectronics, draws
attention to 2D
magnetic silicides. MnSi is a prominent silicide hosting
magnetic phases with unconventional properties; however, little is known about
magnetic states of MnSi at the 2D limit. Here, we explore the magnetism of ultrathin films of MnSi on silicon, down to a single monolayer. Angle-resolved photoemission spectra suggest exchange splitting of MnSi bands. Magnetization measurements confirm that the
ferromagnetic state in MnSi is rather robust with respect to the number of monolayers. Thick metallic films demonstrate the anomalous
Hall effect and negative magnetoresistance; however, as the number of monolayers drops below 3, MnSi becomes an
insulator. Most importantly, the ferromagnetism of ultrathin MnSi films acquires a 2D character, as its effective Curie temperature depends on weak
magnetic fields. The present study establishes MnSi monolayers as 2D ferromagnets that can find potential applications in silicon-based spintronics.
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All authors Yuan Fang, Yang Liu, Dmitry V. Averyanov, Ivan S. Sokolov, Alexander N. Taldenkov, Oleg E. Parfenov, Oleg A. Kondratev, Andrey M. Tokmachev, Vyacheslav G. Storchak
Disordered Systems and Neural Networks
Quantum percolation in honeycomb lattices under random spin-orbit coupling
W. S. Oliveira, Julián Faúndez and Welles Morgado
We investigate
quantum percolation in a honeycomb
lattice with site dilution and random
spin-orbit coupling. Using exact diagonalization combined with finite-size scaling analysis, we study the metal-
insulator transition, extracting the
quantum percolation threshold $p_q$, and the correlation-length exponent, $\nu$. In the absence of
spin-orbit coupling, we find that $p_q$ remains finite and demonstrate that the
quantum threshold is significantly higher than the classical site-percolation threshold $p_c$ of the honeycomb
lattice. When
spin-orbit coupling is present, the spectral statistics exhibit a crossover from the Gaussian orthogonal ensemble to the Gaussian
symplectic ensemble, reflecting the change in
symmetry class. Simultaneously, the
quantum percolation threshold shifts systematically to lower occupation probabilities, indicating that the
spin-orbit coupling favors delocalization. For sufficiently strong
spin-orbit coupling, $p_q$ tends to saturate, while the critical exponent approaches the expected one of the two-dimensional
symplectic universality class.
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Materials Science
Stress field modification near linear complexions increases the effective obstacle size and strengthening effect
Zhengyu Zhang, Daniel S. Gianola and Timothy J. Rupert
Linear complexions are stable defect states that form along dislocations and recent experiments have demonstrated strengthening effects exceeding classical precipitation hardening predictions, motivating a detailed study of nanoscale strengthening mechanisms. Here, molecular dynamics simulations in Al-Cu and Ni-Al face-centered cubic
alloys are used to demonstrate distinct plasticity mechanisms associated with linear complexions. Both nanoparticle array and platelet array complexions exhibit appreciable strengthening. In addition to direct interactions with the particles, stress field modification in nearby regions can restrict dislocation motion as well. Finally, the relative particle-dislocation orientation is found to have a large effect, with the strongest resistance observed when the dislocation stress field aligns with the original complexion nucleation condition. As a whole, these findings provide mechanistic insight into the strengthening observed experimentally and establish design principles for linear complexion-induced strengthening in structural
alloys.
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Materials Science
Topographic patterning in perovskite oxide membranes for local control of strain, nanomechanics and electronic structure
Marti Ramis, Markos Paradinas, Jose M. Caicedo et al. (+3 more)
Single-crystalline perovskite
oxide membranes provide a powerful platform to access physical properties that are inaccessible in bulk
crystals and substrate-clamped thin films. Within this context, the deliberate fabrication of tailored corrugations provides a reliable mean to impose local
curvature enabling deterministic modulation of functional properties. Here, we demonstrate controlled topographic patterning in (00l)-oriented La$_{0.7}$Sr$_{0.3}$MnO$_3$ (LSMO) membranes with thicknesses ranging from 4 to 100 nm where they spontaneously form sinusoidal wrinkles with thickness-dependent periodicity and amplitude. The wrinkle morphology directly modulates membrane stiffness and generates exceptionally large local strains exceeding 5% with strain gradients approaching $\sim$ 2.5 x 10$^{7}$ m$^{-1}$ in the thinnest membranes. These extreme deformations suppress antiferrodistortive octahedral rotations and stabilize polar distortions, evidencing a
curvature-driven
symmetry transformation. The surface potential variation reinforces the formation of wrinkled-induced polar patterns being strongly modulated with thickness. The variation of Mn oxidation state from $\sim$ 3.2+ to $\sim$ 2.85+ provides a direct chemical signature of a thickness-controlled electronic transition. These results demonstrate that corrugation-induced strain gradients in
oxide membranes with different thicknesses can drive coupled structural, nanomechanical and electronic transformations, offering a singular route to engineer their functional states for next-generation electronic devices.
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All authors Marti Ramis, Markos Paradinas, Jose M. Caicedo, Claudio Cazorla, Roger Guzman, Mariona Coll
Mesoscale and Nanoscale Physics
Third-order optical response in d-wave altermagnets: Analytical and numerical results from microscopic model
Shihao Zhang
Altermagnets represent a novel category of
magnetic materials characterized by zero net magnetization yet featuring
spin-split band structures, and they demonstrate distinctive orbital-
spin locking phenomena. Commencing from the minimal multi-orbital tight-binding
Hamiltonian of d-wave altermagnets, we conduct an analysis of the general formulas for the third-order injection and shift currents. These currents are solely determined by the
quantum metric and
quantum connection, being free from Berry
curvature contamination. In the ideal scenario where the $\delta$-bond hopping $V_\delta$ approaches zero ($V_\delta = 0$), we derive closed-form analytical solutions for the third-order photoconductivities. For the general situation with a finite value of $V_\delta$, we present a perturbative analytical solution within the limit of $V_\delta \ll V_\pi$, and this solution is verified through numerical calculations. Our research establishes a comprehensive theoretical description of the third-order optospintronic responses in d-wave altermagnets based on a microscopic model. Moreover, it offers a viable approach for the experimental observation of pure
quantum geometric effects.
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Other Condensed Matter
Spintronic THz emitters based on NiCu alloys
E. A. Karashtin, I. Yu. Pashen'kin, A. V. Gorbatova et al. (+4 more)
We study THz emission from ferromagnet / nonmagnetic material (FM/NM) spintronic nanostructures in which the $Ni_xCu_{1-x}$
alloy with different $x$ is used as an FM, an NM, or both layers. The stoichiometric composition of the NiCu
alloys standing at two positions (we denote it as [FM] or [PM]) is chosen so that it is
ferromagnetic at room temperature in the case it is used as the FM layer, and is paramagnetic at room temperature for the NM layer. Besides, we choose the nickel ratio $x$ close to each other for both [FM] and [PM] types of the
alloy (the difference is only $10\%$). We show that although NiCu[PM] does not contain heavy metal it acts as an effective converter of
spin current into the electric one in our structure showing only 2.8 times smaller efficiency than Pt. Besides, the NiCu[FM]
alloy, despite having quite small Curie temperature (approximately $65 ^\circ C$), acts as an effective
spin source having the efficiency only 2 times smaller than Co in similar structures. This shows up the importance of boundary matching in the spintronic THz sources. Our NiCu-based THz sources reveal a possibility of effective thermally induced control of emission of THz radiation due to a unique combination of high emission rate and relatively small Curie temperature.
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All authors E. A. Karashtin, I. Yu. Pashen'kin, A. V. Gorbatova, E. D. Lebedeva, P. Yu. Avdeev, N. V. Bezvikonnyi, A. M. Buryakov
Materials Science · Cross-listed from physics.app-ph
Automated Design of Tubular Origami with Anisotropic Stiffness
Mingkai Zhang and Davood Farhadi
Thin sheets can be assembled into tubular origami structures that combine deployability with pronounced anisotropic stiffness, enabling applications ranging from robotics to deployable systems. However, most existing tubular origami designs remain limited to degree-four vertex
topologies and are characterized primarily in axial and radial loading modes, without a full assessment of anisotropic stiffness. Here, we present an automated design framework for tubular origami that jointly explores local vertex
topology through generalized degree-$n$ vertices and global tube
topology through the polygonal cross-section, for the systematic design and optimization of anisotropic stiffness. Using a calibrated bar-and-hinge model together with experimental validation, we quantify large-deformation stiffness responses in axial translation, in-plane translation, torsion about the tube axis, and rotation about in-plane axes, thereby characterizing the anisotropic stiffness of the tube across its compliant and constrained deformation modes. The resulting design-space exploration showed that the polygonal cross-sectional
topology is the primary factor governing the anisotropic stiffness. We further show that increasing the local vertex degree can improve global structural performance, particularly for tubes with a small number of cross-sectional vertices, demonstrating that higher local kinematic freedom does not necessarily compromise stiffness at the structural scale. Compared with a
benchmark design, the optimized architectures achieve more than 50 times higher constrained rotational stiffness. Together, these results highlight higher-degree vertices and polygonal cross-sectional
topology as powerful design variables for tailoring anisotropic stiffness in tubular origami.
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Materials Science
Angle dependent hysteretic magnetotransport in MnBi2Te4 nanoflakes
Tithiparna Das and Soumik Mukhopadhyay
Controlling
magnetic phases in two-dimensional systems, where charge transport is highly sensitive to real-space
spin inhomogeneities, is central to understanding emergent
magnetic states in reduced dimensions. In this context, thickness-dependent magnetotransport provides access to irreversible
magnetic processes that are not captured by reversible transport or bulk magnetization alone. Here we report an extensive study of hysteretic magnetoresistance in single-crystalline nanoscale thin flakes of the layered antiferromagnet MnBi2Te4. The multi-step hysteresis exhibits a pronounced non-monotonic dependence on thickness and displays nontrivial angular anisotropy. The transport signatures rule out surface-dominated magnetism and simple bulk metamagnetic transitions as the primary origin. We argue that the
magnetic irreversibility is possibly governed by domain wall pinning and de-pinning processes within a spatially non-uniform
magnetic landscape. These results suggest that reduced dimensionality is a key driver of
magnetic irreversibility in MnBi2Te4.
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Mesoscale and Nanoscale Physics
Supercurrent-induced phonon angular momentum
Takehito Yokoyama
We propose a mechanism of supercurrent-induced
phonon angular momentum in mixed parity
superconductors and s-wave
superconductors with
spin orbit coupling. We derive analytical expressions of
phonon angular momentum induced by the supercurrent by perturbative calculation. The physical interpretation of this effect is also discussed.
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Superconductivity
Robust realization of spin-polarized specular Andreev reflection in V$_2$O-based altermagnets
Yutaro Nagae, Andreas P. Schnyder and Satoshi Ikegaya
We theoretically investigate charge transport in a junction between a conventional
superconductor and a V$_2$O-based altermagnet exhibiting distinctive
spin-split quasi-one-dimensional
Fermi surfaces. The altermagnet is described by a microscopically motivated seven-basis-state model with six-orbital characters that incorporates sublattice degrees of freedom associated with both V and O sites. Based on calculations performed under various boundary conditions, we demonstrate the robust emergence of specular Andreev reflection with a distinctive
spin polarization. Furthermore, we propose an efficient multiterminal setup to detect this specular Andreev reflection through nonlocal conductance measurements. Our results establish V$_2$O-based altermagnets as a promising platform for realizing
spin-resolved Cooper pair splitting, which is essential for generating energy-entangled electron pairs.
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Superconductivity
Surface-induced vortex core restructuring in a spin-triplet superfluid
Riku Rantanen, Mikael Huppunen, Erkki Thuneberg et al. (+1 more)
Observing the structure of quantized
vortices can provide evidence for the pairing nature of a superfluid or
superconductor and pinpoint its order parameter.
Spin-triplet superfluid $^3$He supports a variety of
vortices, calculated and identified so far in bulk fluid. We show numerically that the
vortex core in $^3$He is strongly altered near a surface, resulting in a structure inhomogeneous along the
vortex line. The effect is asymmetric with respect to the relative orientation of the core order parameter anisotropy axis and the surface normal. Coupling of
spin and orbital degrees of freedom in the gradient energy of a triplet order parameter allows the surface to lift the degeneracy of two bulk
vortex states connected by spontaneously broken inversion
symmetry of the core. In a wide range of external conditions, the
vortex structure at the surface is found to be completely different from that in bulk. As an implication, surface-limited
vortex core observations in a triplet-candidate system may not reflect the bulk structure. We propose an experimental verification of the effect by measuring a transition in the
vortex structure in thin slabs of superfluid $^3$He-B.
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All authors Riku Rantanen, Mikael Huppunen, Erkki Thuneberg, Vladimir Eltsov
Materials Science
Cs$_4$Cr$_7$Te$_{10}$: Interwoven Reconstructed Archimedean and Kagome Lattices with a Possible Phase Transition near 130 K
Zhen Zhao, Ruwen Wang, Hua Zhang et al. (+12 more)
Chromium-based materials with complex
lattice geometries provide an important platform for investigating correlated electronic and
magnetic states. However, Cr-based compounds with unusual
crystal geometries are still rarely reported. Here, we report a new Cr-based compound, Cs$_4$Cr$_7$Te$_{10}$, featuring interwoven Cr and Te sublattices that can be viewed as reconstructed networks derived from Archimedean (3.4.6.4) tiling and the kagome
lattice, respectively. Transport measurements reveal the semiconducting nature in Cs$_4$Cr$_7$Te$_{10}$. Magnetization measurements show a weak anisotropy between H//b and H//ac planes, and uncover an anomaly near 130 K that is insensitive to the applied
magnetic fields. Specific-heat measurements further confirm this transition, indicating its bulk thermodynamic nature. The associated
entropy change is as small as 0.41 J mol^-1 K^-1, ruling out a structural phase transition and pointing to a possible electronic and/or
magnetic phase transition. These results provide a new route for designing complex
crystal geometries and exploring their associated emergent phenomena.
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All authors Zhen Zhao, Ruwen Wang, Hua Zhang, Tong Liu, Haisen Liu, Guojing Hu, Ke Zhu, Senhao Lv, Gang Cao, Chenyu Bai, Hui Guo, Xiaoli Dong, Wu Zhou, Haitao Yang, Hong-Jun Gao
Strongly Correlated Electrons
Robust topological surface states in skyrmion-host magnets Eu(Ga,Al)4: evidence for dual topology
Yuki Arai, Kosuke Nakayama, Takemi Kato et al. (+10 more)
The interplay between real-space
topology such as
magnetic skyrmions and momentum-space
topology characterized by topological surface states (TSSs) is predicted to realize novel phenomena and functionalities, yet materials hosting both
topologies are scarce. Skyrmion-hosting helimagnet family EuGa$_2$Al$_2$ and EuAl$_4$ has been a
prime candidate for such a dual-
topology system, but conclusive evidence for its momentum-space
topology has remained elusive. We provide this evidence by directly observing TSSs that stem from bulk Dirac nodal lines using high-resolution angle-resolved photoemission spectroscopy. These TSSs are exceptionally robust against various perturbations such as a 2$\times$1 surface reconstruction, a chemical change in the termination of the
crystal surface, and the onset of helical
antiferromagnetic order. Crucially, below the Neel temperature, we observe replica bands driven by the
magnetic ordering. Moreover, we demonstrate clear surface-termination dependence of this magneto-topological coupling. Our findings establish Eu(Ga$_{1-x}$Al$_x$)$_4$ as a dual-
topology material and offer a rare platform to explore and control the interaction between the two fundamental topological realms.
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All authors Yuki Arai, Kosuke Nakayama, Takemi Kato, Tomonori Nakamura, Asuka Honma, Seigo Souma, Kenichi Ozawa, Kiyohisa Tanaka, Daisuke Shiga, Hiroshi Kumigashira, Yoshinori Okada, Kouji Segawa, Takafumi Sato
Strongly Correlated Electrons
Origin of multiple skyrmion phases in EuAl4
Y. Arai, K. Nakayama, A. Honma et al. (+6 more)
The Dzyaloshinskii-Moriya (DM) interaction has been considered essential for skyrmion formation, however, the discovery of skyrmion
lattices (SkLs) in nominally centrosymmetric materials where the DM interaction is forbidden, such as Eu(Ga$_{1-x}$Al$_x$)$_4$, has challenged this established view. Recent structural investigations of Eu(Ga$_{1-x}$Al$_x$)$_4$ have further complicated this issue by revealing that the charge-density wave breaks local
symmetry, theoretically allowing DM interaction. This raises a fundamental question: are the complex
magnetic phases driven by the DM interaction or by alternative mechanisms? Here, using soft-x-ray angle-resolved photoemission spectroscopy, we determine the three-dimensional bulk electronic structure of Eu(Ga$_{1-x}$Al$_x$)$_4$, and elucidate the electronic origins of its rich
magnetic orders. We directly observe an x-dependent Lifshitz transition leading to the emergence of a
Fermi-surface pocket. Importantly, multiple nesting vectors derived from this pocket match the
symmetries and periodicities of the multiple SkLs. Moreover, these nesting vectors can also account for other
magnetic orders, such as the zero-field helical magnetism, suggesting a common electronic origin of the complex
magnetic phases. These findings suggest that competing nesting-induced Ruderman-Kittel-Kasuya-Yosida interactions and their engineering can generate and control various SkLs and related topological
spin textures.
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All authors Y. Arai, K. Nakayama, A. Honma, S. Souma, D. Shiga, H. Kumigashira, T. Takahashi, K. Segawa, T. Sato
Materials Science
Role of diffusion-induced grain boundary migration during molten salt corrosion of a Ni-30Cr alloy
Konnor Walter, Jagadeesh Sure, Adrien Couet et al. (+1 more)
The response of Ni-Cr
alloys to exposure to molten chloride and fluoride salts is typically characterized by Cr dealloying with the formation of a Cr-depleted bi-continuous porous subsurface layer. The exact mechanism behind the loss of Cr over distances unattainable by
lattice diffusion alone is still debated. To address this question, two different surface finishes, namely electropolished and sanded, of a Ni-30Cr
alloy were exposed to LiCl-KCl-2wt% EuCl3 eutectic salt at 500 {\deg}C for 96 hours. In the absence of fast
diffusion pathways, dissolution occurred layer by layer and was kinetically controlled by Ni dissolution, as observed over the grain interiors of the electropolished sample. Grain boundaries were subject to
diffusion-induced grain boundary migration (DIGM), leading to the formation of pure Ni islands above grain boundaries. This overall behavior contrasted with the sanded surface response that was characterized by several micrometer deep interconnected porosity and complete Cr depletion. DIGM of the dense grain boundaries created by recrystallization of the sanded surface was responsible for the observed sub-surface microstructure. This work unequivocally establishes DIGM as a key mechanism in
alloy molten salt corrosion, and microstructure as a decisive contributor to an
alloy's corrosion response.
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All authors Konnor Walter, Jagadeesh Sure, Adrien Couet, Emmanuelle A. Marquis
Mesoscale and Nanoscale Physics
Torsion-induced confinement and tunable nonlinear optical gain in a mesoscopic electron system
Carlos Magno O. Pereira and Edilberto O Silva
We investigate the optical response of a conduction electron in a helically twisted mesoscopic medium containing a screw dislocation and a uniform torsional background, in the presence of an axial
magnetic field and an Aharonov–Bohm flux. We show that the coupling between longitudinal motion and the
geometric background produces an effective in-plane confinement, allowing bound states to emerge without the need for an external radial potential. Exact analytical solutions are obtained for the energy spectrum and radial wave functions, and these results are used to evaluate linear and third-order nonlinear absorption, changes in the refractive index, the photoionization cross section, and the oscillator strength. The combined action of torsion,
magnetic field, and topological defect increases the interlevel spacing, compresses the radial electronic distribution, and breaks the dynamical
symmetry between opposite angular-momentum channels, leading to strongly asymmetric and state-resolved optical spectra. Under intense optical excitation, the nonlinear contribution can overcome linear absorption, driving the system into a negative-absorption regime and enabling geometry-controlled optical gain. These results establish torsion and defect engineering as effective tools for tuning confinement, resonant energies, and selective amplification in mesoscopic nanophotonic platforms operating in the mid-infrared and terahertz ranges.
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Materials Science
Nonmonotonic Scaling of the Anomalous Hall Effect in a Bicollinear Antiferromagnet
Ruifeng Wang, Chi Fang, Ilya Kostanovski et al. (+5 more)
An anomalous
Hall effect (AHE) in
antiferromagnetic (AF) systems with no net magnetization is of considerable interest for both fundamental physics and spintronic applications. Of particular interest is the two-dimensional van der Waals antiferromagnet FeTe that has an unusual fully magnetically compensated bicollinear AF structure and exhibits pronounced Kondo interaction leading to strong band renormalization. Here, we investigate the AHE in epitaxial FeTe thin films grown by molecular beam epitaxy. A large anomalous
Hall conductivity is exhibited below the Neel temperature (T_N ~ 60 K) and, strikingly, becomes nonlinear at high fields within a narrow temperature window around 49 K, deviating from conventional AHE scaling behavior versus its longitudinal conductivity. Linear fits reveal a pronounced negative peak in the intercept, accompanied by a field-induced canted
magnetic moment. The AHE responses are related to the Berry
curvature derived from FeTe's topological band structure, highlighting the intricate interplay between
topology, magnetism, and electronic transport.
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All authors Ruifeng Wang, Chi Fang, Ilya Kostanovski, Ke Xiao, Felix Küster, Jenny Davern, Naoto Nagaosa, Stuart S. P. Parkin
Mesoscale and Nanoscale Physics
Remote Moiré Modulation of Decoupled Dirac Subsystems in Twisted Trilayer Graphene
Dohun Kim, Junsik Choe, Minseo Cho et al. (+4 more)
Moiré superlattices are generally assumed to act only at the interface where
lattice mismatch or twist occurs. Here, we study charge transport in large-angle helical twisted trilayer
graphene, where interlayer tunneling is strongly reduced. When only the top monolayer
graphene is aligned with hBN, the electronic response reorganizes into a moiré-modulated monolayer and a remaining twisted
bilayer graphene subsystem. Despite the absence of any explicit structural moiré in the twisted
bilayer, we observe satellite-like features in its electronic response that run parallel to the primary spectrum and are locked to the density scale of the hBN/
graphene moiré. These observations are consistent with a weak moiré-periodic electrostatic perturbation generated at the aligned interface and sensed by a spatially separated Dirac subsystem, even in the absence of coherent interlayer coupling.
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All authors Dohun Kim, Junsik Choe, Minseo Cho, Takashi Taniguchi, Kenji Watanabe, Gil Young Cho, Youngwook Kim
Materials Science
Damage dose dependence of deuterium retention in high-temperature self-ion irradiated tungsten
Mikhail Zibrov, Thomas Schwarz-Selinger, Michael Klimenkov et al. (+1 more)
Recrystallized tungsten (W) samples were irradiated by 20 MeV self-ions at 1350 K to peak damage doses in the range of 0.001-2.3 dpa. The irradiation-induced defects were then decorated with deuterium (D) by a gentle D
plasma exposure ($<5$ eV/D, $5.6 \times 10^{19}$ $\text{D} / (\text{m}^2 \text{s})$) at 370 K. The D depth profiles in the samples were measured using $\rm D(^{3}He,p)\alpha$
nuclear reaction analysis. The maximum trapped D concentration evolves differently with the damage dose compared with the previously studied irradiations at 290 K and 800 K. At the damage doses below 0.1 dpa, the D concentrations are lower than those after the irradiation at 800 K. At higher damage doses, the D concentrations exceed the 800 K values and reach 1.7 at.% at 2.3 dpa, showing no clear tendency towards saturation. Transmission electron microscopy revealed the presence of nm-sized voids in the samples irradiated at 1350 K, in contrast to the ones irradiated at 290 K and 800 K. Thermal desorption spectroscopy (TDS) indicates that the dominant D trapping sites are different compared to the irradiations at 290 K and 800 K. Reaction-
diffusion simulations show that the TDS spectra can be described by assuming that D is trapped as $\rm D_2$ gas in the void volume and as D atoms at the void surface.
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All authors Mikhail Zibrov, Thomas Schwarz-Selinger, Michael Klimenkov, Ute Jäntsch
Materials Science
Symmetry breaking structural relaxation and optical transitions of native defects and carbon impurities in LiGa$_5$O$_8$
Klichchupong Dabsamut, Adisak Boonchun and Walter R. L. Lambrecht
LiGa$_5$O$_8$ in a spinel type structure has recently been claimed to be an unintentional p-type ultra-wide-band-gap
oxide semiconductor. While previous computational work did not yet identify the origin of p-type doping and in fact predicted insulating behavior by compensation of deep acceptors by shallow donors, defect characterization in terms of its optical signatures remains important. Rather than focusing on thermodynamics transition levels, as in earlier work, this present paper focuses on the vertical transitions in a defect configuration diagram of defects in different charge states, representing absorption and emission processes involving carrier capture/emission from/to band edges. In addition, the structural relaxation of several native defects is revisited by allowing for more complex
symmetry-breaking distortions in an effort to reconcile conflicting results in the previous literature. Special
attention is given to the Li vacancy because it is the shallowest native acceptor. For this defect, the previously reported transition levels are revised on the basis of
symmetry-breaking relaxations. The structural relaxations, band structures, and densities of states are compared between the
symmetry-broken polaronic and
symmetry-conserving non-polaronic states. Finally, we also study carbon
impurities, which are likely to originate from growth methods involving organic precursors.
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Mesoscale and Nanoscale Physics
Correlation functions for quantum dynamics of coupled quasinormal modes and quantum emitters interacting via finite-delay propagating photons
Robert Meiners Fuchs, Juanjuan Ren, Sebastian Franke et al. (+2 more)
A time-dependent theory for the interactions between spatially separated lossy cavities in a homogeneous background medium using quantized quasinormal modes (QNMs) is presented. The cavities interact via a bath of traveling
photons, described by non-bosonic operators that are orthogonal to the open-cavity QNMs. The retarded (i.e., time-delayed) inter-cavity dynamics are fully described by system-bath correlation functions, in which the emission from one cavity appears as the input field for another. Coupling between
quantum emitters (described as two-level systems), placed inside a cavity or embedded in an external medium, and the electromagnetic field (cavity modes and bath
photons) is included in the theory, which gives rise to both bath-mediated and QNM-mediated interactions between the emitters.
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All authors Robert Meiners Fuchs, Juanjuan Ren, Sebastian Franke, Stephen Hughes, Marten Richter
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Magnetically Tunable Chiral Phonon Polaritons with Magneto-optical Bound States in the Continuum
Yu Sun, Jue Li, Wei Li et al. (+3 more)
Chiral phonon-polaritonic states are of interest for handedness-dependent light-matter interactions, yet their realization and
magnetic control remain challenging, while direct magneto-optical tunability of
phonon-polaritonic media is limited. Here, we propose a hybrid platform in which an hBN
phonon polariton couples to a
chiral bound state in the continuum supported by a magneto-optical photonic
crystal, enabling strong and selective photonic coupling. The interaction gives rise to pronounced mode splitting and the formation of hybrid states, and their modal composition is quantified by
phonon-proportion analysis and described by a coupling theory. Importantly, the hybridization can be controlled by
magnetic bias through the magneto-optical response of the photonic component, providing control over the modal composition and spectral response. In addition, the hybrid states exhibit handedness-selective absorption under circularly polarized excitation. This work offers a feasible route toward magnetically tunable
chiral phonon-polaritonic devices and hybrid polaritonic functionalities
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All authors Yu Sun, Jue Li, Wei Li, Bo Li, Qinghua Song, Mengyao Li
Statistical Mechanics
Finite temperature correlation functions of the sine–Gordon model
M. Tóth, J. H. Pixley, G. Takács et al. (+1 more)
The sine-Gordon model serves as a foundational $1+1$-dimensional
quantum field theory with numerous applications in condensed matter physics. Despite its integrability, characterizing its finite-temperature behavior remains a significant theoretical challenge. Here we use the previously developed Method of Random Surfaces (MRS) to evaluate two-point and higher-order correlation functions. We cross-check these results with known analytical limits, demonstrating that the MRS provides reliable, non-perturbative data in intermediate regimes where traditional form-factor expansions and semiclassical methods are inapplicable. Furthermore, we derive an exact result for arbitrary $N$-point functions satisfying an appropriate selection rule, providing a direct computational method for complex multi-point observables at finite temperature. We also characterize the non-Gaussianity of correlations and demonstrate that the results align with intuitive theoretical expectations.
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All authors M. Tóth, J. H. Pixley, G. Takács, M. Kormos
Materials Science
Electrochemical Performance of Gold Monolayers for Lithium-Ion Batteries: A First Principles Study
Ajay Kumar, Pritam Samanta and Prakash Parida
Being motivated by recent synthesis of a monolayer of gold, named goldene, from the nano-laminated ternary ceramic phase of Ti3AuC2, we are proposing two phases of goldene viz. goldene-I and goldene-II as anode material for Lithium-Ion batteries using first principles study. This innovative goldene-I monolayer, composed of triangular motifs of gold atoms, exhibits remarkable properties owing to its unique
geometric configuration and intrinsic stability. In contrast, a theoretical structure known as goldene-II, featuring a combination of triangular and hexagonal motifs, has been proposed. This structure possesses intrinsic, periodically distributed pores among Au atoms and demonstrates structural integrity and mechanical robustness, even under lithium adsorption. The electronic band spectra and projected density of states reveal the metallic nature of both phases of goldene. Electrochemical evaluations reveal that goldene-II offers favorable lithium-ion adsorption energies, efficient charge transfer, and volumetric capacities. Goldene-I achieves a volumetric capacity of 0.713 Ah/cm3, while goldene-II reaches 0.783 Ah/cm3, confirming its high suitability for lithium storage volumetric capability. Moreover, goldene-I has an ultra-low barrier height of 15 meV, which supports rapid lithium-ion transport.
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Materials Science
Tuning Structure and Magnetism in Large-Scale 2D Ferromagnet Fe$_3$GeTe$_2$ through Ni Doping
Kacho Imtiyaz Ali Khan, Tauqir Shinwari, Soheil Ershadrad et al. (+13 more)
Two-dimensional ferromagnets with strong perpendicular
magnetic anisotropy exhibit
magnetic order down to the monolayer thickness, beneficial for energy-efficient spintronic devices. In this work, molecular beam epitaxy has been employed to realize controlled Ni-doping in Fe$_{3}$GeTe$_{2}$ (FGT) epitaxial films. MBE not only enables a large-scale growth of 2D films, but also allows a precise control over thickness and doping. X-ray diffraction and scanning transmission electron microscopy (STEM) reveal the formation of high-quality epitaxial films of pristine and Ni-doped FGT on
graphene via van der Waals (vdW) epitaxy. Integrated differential phase contrast STEM images further provide in-depth information on Ni substitution and intercalation into the vdW gaps. Ni incorporation in doped films results in the shrinking of both in-plane and out-of-plane
lattice parameters. Superconducting
Quantum Interference Device,
Hall, and X-ray
magnetic circular dichroism measurements were utilized to probe the
ferromagnetic properties of the films. Due to both Ni substitution and intercalation into the vdW gaps for Ni-doped FGT films, we observed a suppression of PMA and a drastic reduction in the Curie temperature down to 50 K. Our density functional theory based calculations of structural and
magnetic properties further supports and provide deep insights into the variations of
magnetic exchange interaction parameters and atom-projected magnetocrystalline anisotropy energies due to Ni doping to understand the experimental observations.
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All authors Kacho Imtiyaz Ali Khan, Tauqir Shinwari, Soheil Ershadrad, Majid Ahmadi, Weiben Li, Hua Lv, Frans Munnik, Adriana I. Figueroa, Manuel Valvidares, Sandra Ruiz-Gómez, Lucia Aballe, Jens Herfort, Michael Hanke, Bart Kooi, Biplab Sanyal, João Marcelo J. Lopes