Materials Science
Numerical modeling of microstructure evolution in nanocrystalline alloys - grain boundary segregation, solute drag and mechanics
Prakarsh Pandey and Shiva Rudraraju
Nanocrystalline (NC)
alloys hold much promise as structural
alloys due to their superior mechanical properties over traditional coarser grained microcrystalline
alloys. Strength of metallic
alloys is related to the underlying grain size - as represented by the classical
Hall-Petch relation. Generally, a metals strength increases with decreasing mean grain size from the micrometer scale to the nanometer scale, until about a mean size of 20 nm. Any further decrease of grain size results in decreasing strength. Thus, there is an optimal range of mean grain size for most metals about which maximum material strength can be obtained. In the context of NC
alloys, stabilization of the grain size in this optimal range is one of the primary synthesis challenges. Since nm-scale mean grain sizes are desired, phenomena like GB solute segregation and solute precipitation are utilized during
alloy synthesis to mitigate grain growth. Numerical modeling the phenomena of GB-solute interactions and the
evolution of these stabilized GBs under mechanical load are of immense interest to the NC
alloy community. To enrich the numerical modeling formulations available in this space, we present here a phase-field method based numerical framework to model GB segregation, solute precipitation and effect of external loading on NC
alloys. While some of these effects have been modeled in isolation, a unified treatment of the solute and GB segregation with mechanics interactions has not be considered in the literature. We present a 3D FEM finite-strain phase-field formulation for modeling grain
evolution and microstructure stabilization. Beyond the formulation, various case studies demonstrate the applicability of this framework. Further, thermodynamic and kinetic arguments are provided based on the
evolution of GB energy to explain the effects of solute drag, GB pinning and mechanical deformation.
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Other Condensed Matter
Analytic Boundary Terms for Arbitrary Crystal Geometries and Direct-Sum Evaluation of Madelung Constants in Triclinic Lattices
Yang He and Zhonghan Hu
The direct-sum evaluation of Madelung constants is complicated by the conditional convergence of
lattice sums, which gives rise to a shape-dependent boundary term. In this work, we present, for the first time, a closed-form analytic expression for this boundary term that is valid for arbitrary
crystal geometries. For general triclinic
lattices, this boundary term maps exactly onto the electrostatic potential generated by a set of uniformly charged parallelograms. In addition, we demonstrate that the residual finite-size correction for a
crystal of characteristic size $p$ decays as $(2p+1)^{-2}$. Building on these results, we develop a robust direct-sum method for the accurate computation of Madelung constants in arbitrary triclinic
lattices and validate its effectiveness through explicit calculations on representative Bravais
lattices.
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Mesoscale and Nanoscale Physics
Complete kinematic null for local kinetic dissipation in a sixfold-driven electron fluid
P. Shubham Parashar
We identify a complete kinematic null in a two-dimensional electron fluid driven by a sixfold boundary pattern. In the $U_3^\pm$ channel of $D_{12}$, device
symmetry excludes both the vector representation $R_1$ and the full first-gradient tensor $R_1\otimes R_1$. Hence at the
symmetry-fixed center $\mathbf{j}(0)=0$ and $\partial_i j_j(0)=0$, so every local quadratic dissipative form built from the modeled charge/momentum field through first gradient order vanishes independently of the constitutive coefficients. In an $O(2)$-isotropic angular-harmonic kinetic model the first allowed local sector is $m=3$. For $\nu q^2/\gamma_3\ll1$, its heating is set by the previously derived coefficient $\kappa_4=v_F^4/(16\gamma_2^2\gamma_3)$. An explicit incompressible Stokes disk realizes a nonzero center signal, and a finite-moment kinetic boundary-value solution approaches the corresponding local
benchmark. Within the local, fixed-current momentum-conserving Stokes regime, the normalized
magnetic response can then be fitted for effective $\gamma_3$ and $\gamma_2$. Thus the sixfold drive creates a measurement point where ordinary local charge/momentum hydrodynamic dissipation is absent while a kinetic mode remains finite.
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Strongly Correlated Electrons
Cell Natural Orbitals in Interacting Topological Bands
Nishchhal Verma, Harshitra Mahalingam, Daniel Muñoz-Segovia et al. (+1 more)
Topological bands exhibit obstruction to exponentially localized and symmetric Wannier functions, challenging the standard paradigm of representing projected interactions in terms of local orbitals with finite range. To faithfully capture the form factors and
quantum geometry of topological bands we introduce a singular-value decomposition of the band-projected density form factors, enabling a geometry-based truncation scheme of the
Hilbert space, exposing an intrinsic hierarchy on band-projected interactions that is determined by the underlying wavefunctions. This decomposition is most naturally described in terms of
Cell Natural Orbitals (CNOs), as the eigenstates of the unit-
cell reduced one-particle density
matrix, whose occupation provide a measure of the minimal orbital complexity required to faithfully represent the band wavefunctions overlaps. The CNO decomposition identifies systematically the minimal number of local orbitals needed to reproduce short-ranged interactions while resolving the hierarchy of interaction strengths across CNO channels. Applied to magic-angle twisted
bilayer graphene in the
chiral limit, we find that the dominant CNO is centered at the AA site, resembling the $f$-
fermion of the heavy-
fermion model. The subdominant CNO channels carry progressively weaker interaction
matrix elements, allowing them to be treated at the static mean-field level, while the dominant channel requires a dynamical self-energy. The formalism illustrates how variations of charge density within the unit
cell generate momentum dependence in the CNO envelope function and, consequently, dispersion in the single-particle spectral function. More broadly, our results establish CNOs as a geometry-informed bridge between band
topology and real-space correlations, providing a systematic framework for analyzing interactions and emergent phases in
quantum materials.
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All authors Nishchhal Verma, Harshitra Mahalingam, Daniel Muñoz-Segovia, Raquel Queiroz
Quantum Gases · Cross-listed from quant-ph
A Quantum Coherence Microscope in the Hubbard Regime
Lin Su, Michal Szurek, Alec Douglas et al. (+2 more)
Quantum coherence underlies collective
quantum phenomena and emerging
quantum technologies.
Quantum gas microscopes have transformed
quantum simulation by providing projective snapshots of many-body states with single-atom resolution, but spatially resolved measurements of off-diagonal correlations have remained elusive. Here, using the Talbot effect, we introduce a
quantum coherence microscope that maps off-diagonal correlations onto site-resolved density signals with near-single-site resolution. We use this technique to locally probe the superfluid-Mott transition in a layer of a three-dimensional optical
lattice and to measure coherence beyond nearest neighbors in an engineered potential landscape. By mapping off-diagonal correlations onto density signals through controlled Talbot
evolution, this work opens new possibilities for accessing observables beyond the density basis through tailored matter-wave
evolution and recapture.
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All authors Lin Su, Michal Szurek, Alec Douglas, Ceren B. Dag, Markus Greiner
Strongly Correlated Electrons · Cross-listed from hep-th
The quadratic growth of Krylov spread complexity in the BTZ black hole
Aranya Bhattacharya, Mario Flory, Michal P. Heller et al. (+2 more)
The boundary quantity that captures the growth of black-hole interiors quantified by
holographic complexity remains unknown beyond 2d dilaton
gravity. We provide a critical analysis of a partition-function construction of Krylov spread complexity for thermofield-double states that provides a dimension-independent boundary reconstruction from semiclassical
holographic partition functions, while developing the present dynamical and bulk construction for the BTZ saddle. In the double-scaled Sachdev-Ye-Kitaev model, where exact and semiclassical results can be compared, we show that the classical limit is reliable only when taken after the complexity has been reconstructed; taking this limit at the level of individual Lanczos coefficients discards essential information. Applying the construction to a large-central-charge two-dimensional conformal field theory above the Hawking-Page temperature dual to a Bañados-Teitelboim-Zanelli black hole, we find an intermediate departure from early-time quadratic growth followed by behavior compatible with a return toward asymptotically quadratic growth, rather than the linear late-time behavior of the volume and the standard finite-functional complexity = anything class. We then match this boundary behavior to a generalized complexity = anything bulk object built from an infinite series of extrinsic-
curvature invariants. The construction provides a systematic route from black-hole thermodynamics to Krylov dynamics and can naturally be extended to higher-dimensional
holographic black holes.
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All authors Aranya Bhattacharya, Mario Flory, Michal P. Heller, Emiliano Rizza, Tim Schuhmann
Materials Science
AES-Debye: an Accurate, Efficient, and Scalable Engine for Debye Scattering Calculations
Navid Panchi, Sebastian Kuckuk, Markus Wittmann et al. (+2 more)
Total scattering models are essential for characterizing the structure and disorder of nanoscale materials. The Debye scattering equation (DSE) provides a rigorous route to elastic total scattering, but its direct evaluation is computationally demanding because pairwise contributions must be accumulated at every scattering vector, whereas common acceleration strategies based on binned pair-distance distributions or gridded fast
Fourier transforms can introduce discretization and aliasing artifacts that compromise diffuse-scattering accuracy. Here, we present AES-Debye, an accuracy-preserving DSE framework that aggregates pair distances into a pair distribution function (PDF) using corrected bin centers and numerically robust accumulation to suppress discretization and summation errors. A data-locality-aware parallel design enables efficient execution on CPUs and GPUs. We demonstrate strong scalability by computing a high-resolution total scattering profile for a system of 90 million atoms, $(0.1,\mu\mathrm{m})^{3}$, in minutes on a distributed-
memory CPU platform. These capabilities extend accurate elastic total scattering calculations to large, complex systems while simultaneously providing high-resolution PDFs for downstream structural analysis.
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All authors Navid Panchi, Sebastian Kuckuk, Markus Wittmann, Michael Engel, Alberto Leonardi
Strongly Correlated Electrons · Cross-listed from quant-ph
Decoupling 2D translation-invariant topological CSS codes
Yifei Wang, Zhongyi Ni, Mingxin He et al. (+2 more)
Two-dimensional translation-invariant topological CSS codes on
qubits are known to be locally equivalent, after coarse-graining, to stacks of toric codes. However, existing constructions generally break more translation
symmetry than is required to remove anyon-permuting translations, leaving open whether any further obstruction exists. We prove that no such obstruction occurs: after passing to the maximal anyon-preserving superlattice, every such code admits a local
unitary decoupling into toric codes and product states. We further provide an efficient
algorithm for explicitly constructing the decoupling map, together with bounds on the required supercell size and operator spreading. The decoupling requires no additional ancillas in generic cases and extends to finite systems with suitable boundary conditions.
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All authors Yifei Wang, Zhongyi Ni, Mingxin He, Jinguo Liu, Yingfei Gu
Strongly Correlated Electrons · Cross-listed from quant-ph
From Koszul-Complex Stabilizer Models to Superselection Profiles: Topological Rigidity and Nonsplit Extensions
Hao Song
Koszul-complex stabilizer models unify the toric-code hierarchy and bivariate-bicycle codes in one homological framework. To study translation-
symmetry-enriched topological (SET) phases in these models and, more generally, in translation-invariant Calderbank-Shor-Steane (CSS) codes with stabilizer maps $(\varphi_X,\varphi_Z)$, we introduce the associated topological superselection profile $\mathscr S_\sigma:=\tau_{\geq1}\mathbf R\!\operatorname{Hom}_R(\overline{\operatorname{coker}\varphi_\sigma},R),\ \sigma=X,Z$. Its
cohomology layers $E_\sigma^\ell:=H^\ell(\mathscr S_\sigma)\cong_R\operatorname{Ext}_R^\ell(\overline{\operatorname{coker}\varphi_\sigma},R)$ encode sectors, fusion, and translation action. When finite, the $\ell=1,2,\ldots$ layers describe pointlike, looplike, and higher-dimensional excitations; $\mathscr S_\sigma$ retains inter-layer gluing. For regular Koszul models, we compute $E_\sigma^\ell$ explicitly, find $\mathscr S_\sigma$ single-layer, and obtain finite-size $Z$-logicals from $\operatorname{Tor}$. Single-layer means that at most one positive-degree layer $E_\sigma^\ell$ is nonzero. Our
matrix-level Schanuel-lemma method proves
rigidity: under a finite-resolution hypothesis, the nonzero layer and degree uniquely determine a topological CSS code's translation SET order at the stable translation-invariant Clifford level. For
prime qudits the hypothesis is automatic, and a finite layer's translation kernel gives the exact minimal coarse graining to a toric-code stack. We realize admissible single-layer data. Beyond this regime, split and nonsplit extensions of 3D
qubit toric codes yield eight models sharing all identical $E_\sigma^\ell$ layers with trivial translation action but having distinct size-dependent ground-state degeneracies, hence distinct translation SET phases. Thus inter-layer gluing carries SET data invisible to individual layers.
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Strongly Correlated Electrons
Tunable Multiband Geometry and Fractional Phases in Higher Vortexable Systems
Xiaohan Wan, Siddhartha Sarkar, Ting Cao et al. (+3 more)
Higher vortexability is often viewed as a route to topological flat bands with higher-Landau-level-like
quantum geometry. Here we emphasize a complementary perspective: it provides a tunable multiband structure in which wave function geometry can be varied continuously while the band dispersion, degeneracy, and
topology remain fixed. We perform systematic exact-diagonalization studies of many-body phases in fractionally filled higher vortexable moiré systems, retaining the full flat-band
Hilbert space rather than projecting onto a single band. The multiband treatment reveals a cascade of Abelian and non-Abelian phases at zero
magnetic field, including integer and fractional
exciton insulators, Abelian fractional Chern
insulators, Moore-Read and Read-Rezayi states. At fixed filling, different phases are connected through transitions or crossovers driven solely by changes in wave function geometry, highlighting
quantum geometry itself as a direct tuning parameter between competing topological states. At fillings associated with Moore-Read and Read-Rezayi states, our calculations show that interband mixing shifts the optimal
quantum geometry regime without suppressing non-Abelian topological order under screened Coulomb interaction. Our results establish higher vortexable moiré bands as a tunable platform for exploring geometry-driven multiband topological phases at zero
magnetic field.
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All authors Xiaohan Wan, Siddhartha Sarkar, Ting Cao, Mark Rudner, Di Xiao, Kai Sun
Materials Science
Substrate-dependent thermally driven morphological evolution of Pt$_{0.9}$Ni$_{0.1}$ thin films on sapphire and langasite
M. Awais Fiaz, M. Greenslit, R. J. Lad et al. (+3 more)
We examine the thermal
evolution of 100-nm-thick Pt$_{0.9}$Ni$_{0.1}$
alloy films on sapphire and langasite substrates with a 10-nm Zr adhesion layer. Sequential
vacuum annealing from room temperature to 800 $^\circ$C produces a substrate-dependent morphological pathway that is quantified by atomic force microscopy, image
segmentation, height-distribution analysis, and effective coarsening metrics. Both types of films remain densely granular up to 400 $^\circ$C, undergo a sharp coarsening transition between 400 and 600 $^\circ$C, and evolve into coalesced faceted crystallites by 800 $^\circ$C. The mean projected feature area increases from $7.84 \times 10^2$ to $1.09 \times 10^5$ nm$^2$ on langasite and from $3.32 \times 10^2$ to $1.67 \times 10^5$ nm$^2$ on sapphire. Sapphire therefore develops the larger faceted crystallites, while langasite exhibits the larger roughness maximum at 600 $^\circ$C. Area distributions reveal that the 400-600 $^\circ$C transition does not uniformly shift the initial granular population but instead replaces it with a distinct large-feature ensemble. Height and roughness measurements show a pronounced maximum at 600 $^\circ$C, followed by partial smoothing at 800 $^\circ$C, consistent with rapid coalescence followed by faceting-limited growth. An effective Arrhenius analysis based on $\Delta\langle r^2\rangle$, with $\langle r^2\rangle = \langle A\rangle/\pi$, identifies the 400-600 $^\circ$C interval as the dominant coarsening window. These results show that the thermal stability of PtNi/Zr films on sapphire and langasite is governed by the coupled influence of
alloy mobility, interfacial energetics, and substrate-dependent morphological selection.
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All authors M. Awais Fiaz, M. Greenslit, R. J. Lad, Mauricio Pereira da Cunha, Luke Doucette, S. M. Hollen
Materials Science · Cross-listed from astro-ph.SR
Infrared Spectroscopy and Photochemistry of Aromatic Nitriles in Para-Hydrogen Matrices
Sam McGrath, Vincent J. Esposito, Linshan Zeng et al. (+6 more)
Motivated by recent detections of several aromatic nitriles in Taurus Molecular Cloud-1, we report laboratory and theoretical investigations of the vibrational spectroscopy and photochemistry of singly and doubly cyano-substituted benzene in solid para-hydrogen
matrices. We compare the photochemistry of cyanobenzene (benzonitrile) and three dicyanobenzene isomers initiated by excitations at 193 nm. In addition, we report the photochemistry of deuterated cyanobenzene (d$_5$-cyanobenzene), enabling us to determine the major products produced during the cyanobenzene photodissociation. The major products observed in the photolysis of all the nitriles are HCN and HNC, which are likely produced by hydrogen abstraction from para-H$_2$ by the CN radical. This indicates that the major photodissociation channel involves cleavage of the bond between the ring and the nitrile group, forming the phenyl (or cyanophenyl) radical + CN. We observe secondary photoproducts similar to those found during benzene photolysis. Our findings may aid the interpretation of recent JWST mid-infrared observations of aromatics in photodissociation regions.
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All authors Sam McGrath, Vincent J. Esposito, Linshan Zeng, Thomas H. Speak, Brendan Moore, Pavle Djuricanin, Jun Miyazaki, Takamasa Momose, Ilsa R. Cooke
Strongly Correlated Electrons
Anomalous temperature dependence of polaron mobility in a nonlinear double-well potential: unbiased X-propagator approach
Stefano Ragni, Osor S. Barišić, Naoto Nagaosa et al. (+1 more)
We develop an unbiased X-propagator method for calculating finite-temperature optical conductivity $\sigma(\omega)$ and dc mobility $\mu$ for arbitrary nonlinear electron-
phonon interaction. We apply it to a polaron coupled to a double-well
lattice potential, a minimal model for strongly anharmonic polar materials. At moderate coupling, the mobility exhibits three temperature regimes associated with confinement within one well, thermal competition with the barrier, and barrier-insensitive high-temperature dynamics. This sequence produces a concave temperature dependence of the mobility that is absent in conventional linear-coupling polaron models. At strong coupling, the mobility becomes nonmonotonic, and its temperature
evolution is reflected in a characteristic redistribution of optical spectral weight. For parameters relevant to SrTiO$_3$, our results qualitatively reproduce both the anomalous concave mobility and the onset of violation of the Mott-Ioffe-Regel limit, thereby supporting nonlinear coupling to a soft anharmonic
lattice mode as a microscopic mechanism for anomalous transport in dilute polar metals.
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All authors Stefano Ragni, Osor S. Barišić, Naoto Nagaosa, Andrey S. Mishchenko
Mesoscale and Nanoscale Physics
Topological phase rectification via Aharonov-Bohm interference in a Majorana–quantum-dot interferometer
Jia Liu, Hao-Yuan Yang, Yuan Hong et al. (+5 more)
We propose and theoretically investigate a topological superconducting rectifier based on a
quantum-dot–Majorana interferometer. The Aharonov-Bohm phase, controlled by a
magnetic flux threading the interferometer loop, tunes the
quantum interference between a trivial $2\pi$-periodic
quantum-dot channel and a topological $4\pi$-periodic Majorana channel. At non-integer flux, this interference generates a persistent current background $I_{\rm off}$ that shifts the current-phase relation into a unipolar regime, in which the supercurrent flows strictly in one direction. We introduce a signed unipolarity factor $\eta_u$, with $|\eta_u|>0.5$ defining the unipolar regime, and establish its quantitative relationship to the conventional diode efficiency $\eta$. The unipolarity proves robust against variations of the
quantum-dot level,
spin polarization, and Majorana hybridization, is enhanced by stronger Majorana coupling and Rashba
spin-orbit interaction, and persists at realistic temperatures and under quasiparticle poisoning. We further propose a topological diode figure of merit $\mathcal{Z}_{\rm TD}$, defined from the
Fourier spectrum of $\eta_u$, whose nonzero value provides a model-independent signature of the $4\pi$-periodic Majorana channel and distinguishes topological from trivial rectification mechanisms. Our findings establish the
quantum-dot–Majorana interferometer as a promising route toward high-performance topological superconducting diodes with clear experimental signatures accessible via standard dc transport measurements.
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All authors Jia Liu, Hao-Yuan Yang, Yuan Hong, Li Ma, Feng Chi, Zi-Chuan Yi, Li-Ming Liu, Zhen-Guo Fu
Materials Science
Spatially resolved elastic strain and lattice rotation at threading dislocations in HgCdTe/CdZnTe epilayers by dark-field X-ray microscopy
C. Yildirim, A. Benhadjira, P. Ballet et al. (+5 more)
Threading dislocations (TDs) propagating from a Cd$_{1-y}$Zn$_{y}$Te (CZT) substrate into a
liquid-phase-epitaxy Hg$_{1-x}$Cd$_{x}$Te (MCT) epilayer set the minority-carrier lifetime and dark-current floor of mid-wave infrared focal-plane arrays, yet at device-grade densities their local strain fields have been accessible only through topography, which conflates
lattice tilt and elastic strain. We apply dark-field X-ray microscopy in reflection geometry to a \SI{7}{\micro\metre}-thick (111) MCT/CZT epilayer. Shallow Bragg angle and absorption makes the signal layer dominated while the numerical aperture of the objective keeps the layer and substrate rocking curves convolved, so weak-beam images on either side of the rocking curve and their difference image the correlated defects in a single frame: dot-like substrate TDs and the elongated, in-plane island features they nucleate in the layer. Kernel average misorientation resolves each TD as a \SI{7}{\micro\metre} signature, the layer thickness, alongside axial strain lobes of $\pm(4$ to $5)\times10^{-5}$.
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All authors C. Yildirim, A. Benhadjira, P. Ballet, T. N. Tran Caliste, J. Baruchel, C. Detlefs, D. Brellier, M. P. Kabukcuoglu
Materials Science
Polar-vortex-driven interfacial strain coupling in PbTiO3/SrRuO3 Heterostructures
S. A. Raza, V. A. Stoica, H. Zheng et al. (+7 more)
Interfacial coupling in
oxide heterostructures is a central problem in condensed-matter physics, as it typically emerges at the atomic scale through local interactions mediated by
lattice polarization and strain. In this work, we investigate nanoscale polar-supertexture-driven interfacial strain coupling in (PbTiO3)16/(SrRuO3)9/(PbTiO3)16
heterostructures grown on DyScO3(110) substrates. Under appropriate epitaxial strain conditions, the PbTiO3 layers form polar
vortex superstructures with a periodicity of approximately 10 nm. We demonstrate that the resulting in-plane nanoscale strain modulation propagates into the SrRuO3 layer. Using element-specific resonant X-ray reflectivity, we probe the nanoscale strain modulations of the strontium and ruthenium sublattices at the interface, revealing strong interfacial strain coupling between the ferroelectric and
ferromagnetic layers. These findings provide new insights into engineering nanoscale
magnetic modulations through interfacial strain and polarization control.
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All authors S. A. Raza, V. A. Stoica, H. Zheng, H. G. Lee, A. Ross, U. Saha, L. Q. Chen, L. W. Martin, V. Gopalan, J. W. Freeland
Materials Science
Predictive Simulation of Interphases on Li Metal Surface
Xinyu Li, Jingxuan Ding, Daniel C. Hannah et al. (+3 more)
Interphases remain the least understood components in advanced batteries. Although their properties dictate whether a new battery chemistry could perform as designed, there has never been a reliable way to predict what an interphase could arise from a new electrolyte system due to the absence of atomistic level knowledge about interphasial formation process. In this work, we attempt to develop a simulation method that can universally predict interphasial chemistries formed on Li metal surface, so that the electrolyte engineering would no longer need lengthy Edisonian approaches. By combining a transferable universal polarizable force field and a universal machine learning force field, we simulate interphasial chemistry across chemically diverse electrolyte formulations, and successfully replicate the experimental observation that fluorinated solvents promote the formation of LiF-rich interphases, whereas interphases of more organic origin arise from conventional carbonate-based electrolytes. By directly capturing these spontaneous interfacial reactions behind these interphasial chemistries, our simulations establish molecular-level relationships between electrolyte chemistry, salt concentration, decomposition pathways, and SEI properties, and opens a route toward universal and high-throughput predictive simulation of interphases that is the foundation for AI-driven electrolyte discoveries.
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All authors Xinyu Li, Jingxuan Ding, Daniel C. Hannah, Yumin Zhang, Qichao Hu, Kang Xu
Superconductivity
Superconductivity, pseudogap and marginal Fermi liquid in a relative-momentum-local theory
Jian-Jian Miao
Cuprate
superconductors host \(d\)-wave superconductivity (SC), a pseudogap (PG) with
Fermi arcs and a strange metal (SM) with incoherent excitations and temperature-linear resistivity. These regimes emerge from the same doped Mott system but are usually described separately. Here a relative-momentum-local (RML) theory is constructed, with the exact
spin-singlet Cooper representation of
antiferromagnetic superexchange in the \(t\)-\(J\) model serving as a common thread. Pair correlations organize the low-energy behaviour of this Cooper channel into phase-coherent static SC, phase-incoherent quasi-static PG and phase-incoherent dynamic SM. A static RML prescription yields an exactly solvable PG
Hamiltonian with nodal electron poles, antinodal gaps, resolution-broadened
Fermi arcs and gapless charge-\(2e\) Cooper surfaces. A Cooper-surface Lifshitz transition generates logarithmic enhancements in the specific-heat coefficient and charge response without a
spin singularity. The particle-particle continuum at finite centre-of-mass momentum produces Ohmic damping, while a dynamic RML prescription yields a one-loop self-energy with marginal-
Fermi-
liquid scaling. Spectral-weight transfer in the physical pair spectrum diagnoses the PG–SM crossover, whereas nonzero phase stiffness and global phase coherence identify SC. The RML theory relates single-particle, pair-sensitive and thermodynamic probes to three infrared organizations of one Cooper channel. A decisive experimental signature would be zero-energy Cooper-surface ridges in two-electron angle-resolved photoemission spectroscopy (2e-ARPES).
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Mesoscale and Nanoscale Physics
Disorder-robust trivial Majorana-like states from smooth confinement in chiral superconducting nanowires
Eslam Ahmed, Jorge Cayao and Yukio Tanaka
Near-zero-energy states in Majorana nanowires can arise from topologically trivial mechanisms such as smooth spatial inhomogeneity and disorder, making zero-energy pinning alone insufficient evidence of bulk
topology. Here we identify a real-space mechanism governing their robustness to
symmetry-preserving disorder. For a
chiral-symmetric Bogoliubov-de Gennes
Hamiltonian, we decompose a low-energy state into two normalized components of opposite chirality and show that disorder-induced splitting is bounded by their spatial overlap. We demonstrate this result in a finite Rashba nanowire with smooth chemical potential and pairing profiles. Below the bulk topological transition, smooth confinement produces partially separated
chiral components with exponentially small overlap, yielding globally trivial Majorana-like Andreev bound states that remain near zero energy even under strong scalar, nonmagnetic disorder. The
chiral overlap therefore provides a direct diagnostic of the protection of low-energy states against local perturbations, independent of the bulk topological invariant.
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Mesoscale and Nanoscale Physics
Probing crystal-field modulations with magnetic adatoms on the incipient charge-density-wave superconductor $2H$-NbS$_2$
Werner M.J. van Weerdenburg, Margarete Huisinga, Constantin Flommersfeld et al. (+2 more)
The interplay between multiple
quantum phases in layered materials may lead to incipient
quantum behavior, where the material's ground state is close to a phase transition and sensitive to local disorder. The transition metal dichalcogenide material $2H$-NbS$_2$ exhibits incipient charge-density-wave behavior along with a well-developed superconducting state, creating a scenario where the local
lattice instabilities play a crucial role. Here we present how an individual
magnetic atom on $2H$-NbS$_2$ can be applied as a local sensor to reveal hidden
crystal-field modulations. By manipulating the adatom across the surface with the tip of a scanning tunneling microscope, we measure variations in the Yu-Shiba-Rusinov (YSR) excitation spectra and map the local environment around an intrinsic point defect. We find that while the superconducting state is spatially uniform, the YSR excitation energy strongly depends on the position of the atom. We determine that the main contribution to this effect originates from variations in the local
crystal-field environment. These results establish a new approach to investigate
crystal-field modulations at the atomic scale and reveal how defects and
lattice instabilities shape the atomic landscape of an incipient charge-density-wave material.
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All authors Werner M.J. van Weerdenburg, Margarete Huisinga, Constantin Flommersfeld, Lisa M. Rütten, Katharina J. Franke
Superconductivity
Revealing Hidden Unconventional Pairing through Nonreciprocal Transport
Wen-Bo Dai, Ming Gong, Xianxin Wu et al. (+2 more)
Identifying the pairing
symmetry of Cooper pairs is a fundamental step toward understanding the microscopic mechanisms of unconventional
superconductors. However, experimental identification remains a formidable challenge, particularly when unconventional pairing is obscured by a dominant $s$-wave component that masks its spectroscopic signatures. Here, we develop a
symmetry-resolved framework to identify superconducting pairing
symmetry through nonreciprocal conductance upon exchanging source and detector terminals in multiterminal devices. We show that nonreciprocal transport arises from
symmetry-breaking components of the superconducting order parameter and exhibits a characteristic angular dependence that encodes the momentum-space structure of the pairing gap. In particular, time-reversal-breaking singlet pairing induces nonreciprocal charge transport, while
spin-triplet pairing generates nonreciprocal
spin responses, providing distinct transport fingerprints of the underlying order. We demonstrate this mechanism using representative models of iron-based and noncentrosymmetric
superconductors and outline experimental protocols for multiterminal measurements. Our results advance the theoretical understanding of nonreciprocal transport in
superconductors, and establish it as a
symmetry-selective probe for identifying hidden unconventional pairing in a wide range of superconducting materials.
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All authors Wen-Bo Dai, Ming Gong, Xianxin Wu, Chui-Zhen Chen, X. C. Xie
Strongly Correlated Electrons · Cross-listed from quant-ph
Quantized Stabilizer-Rényi Boundary Response across Fermionic SPT Transitions
M. A. Rajabpour
Open boundaries host
symmetry-protected Majorana modes, yet their imprint on the stabilizer Rényi
entropy is obscured by a nonuniversal volume law. At Rényi index $\alpha=1/2$, we isolate a bulk-subtracted boundary response in free-
fermion BDI chains using exact finite-open-chain relations, large-$L$ Pfaffian evaluations, and direct positive-weight checks. Across a mass inversion, this response approaches $|\Delta\omega|\ln 2$, where $\Delta\omega$ is the change in winding number. The response survives primitive bulk deformations, the tested local boundary perturbations, and broken bulk duality. Thus, for the families studied here, the boundary response counts the Majorana channels that change the fermionic SPT index.
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Statistical Mechanics
Sampling Free Energy Landscapes of Ionic Colloidal Crystal Systems using Machine-Learned Proxy Collective Variables
Michael S. Chen, Stefano Sacanna and Glen M. Hocky
Charged colloids coated with a
polymer brush can be designed to preferentially self-assemble into different
crystal structures by varying easy-to-tune experimental conditions. For a given set of conditions, we have observed in experiments and simulations a distribution of thermodynamically (meta)stable self-assembled
crystal structures. Properly quantifying the free energy landscape of these colloidal systems is essential for rationally choosing conditions to preferentially target particular
crystal structures. For some of the structures we have formed, standard crystalline order parameters are not able to differentiate between
crystals or between
crystals and amorphous aggregates. We show that local environment similarity descriptors are able to distinguish the relevant metastable states, but are too expensive for use in biased MD simulations. Here, we adopt an approach from machine-learned interaction potentials showing that SE(3)-equivariant
transformer networks can serve as an efficient-to-evaluate machine-learned proxy. As a result, we can compute the relative free energies of accessible colloidal structures as a function of different experimentally-relevant physical knobs that can steer our system between two observed
crystal types. As an example application, we then show how changing surface potentials of positive and negative colloids while maintaining the same attractive energy can shift which
crystal structure is favored.
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Statistical Mechanics · Cross-listed from quant-ph
State Diagnostics of Complexity in Open Quantum Systems
Komal Sah, Fabio Anza, Alexandra M. Jurgens et al. (+1 more)
We study the emergence of complexity in finite-size
quantum systems as their dynamics transition from closed and coherent
evolution to interacting and effectively open behavior. Using a state-based
geometric framework, we represent mixed
quantum states as probability measures on complex projective
Hilbert space. This representation allows us to track how interactions reshape the underlying pure-state geometry. We introduce two complementary diagnostics: a distinguishability measure, based on the Wasserstein distance between probability-measure representations of mixed states, that quantifies sensitivity to initial states, and a state-space coverage index that measures long-time exploration of the subsystem state space. These diagnostics provide a
geometric perspective on the emergence and
evolution of
quantum dynamical complexity. When applied to the
quantum kicked top, both diagnostics generally increase with interaction strength. Their dependence on environment size is structured by parity
symmetry, with integer-
spin systems often exhibiting greater sensitivity and state-space coverage than half-integer-
spin systems. These results highlight finite-size
quantum effects and provide a
geometric approach to quantifying dynamical complexity deep in the
quantum regime
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All authors Komal Sah, Fabio Anza, Alexandra M. Jurgens, James P. Crutchfield
Statistical Mechanics · Cross-listed from quant-ph
Spread of Entanglement in Generalized Kicked Ising Chain
Tanay Pathak, Hiromi Ebisu and Tomaž Prosen
We investigate the dynamics of
entanglement in a generalized version of the kicked Ising chain, extending the model from the standard
qubit case (local dimension $q=2$) to higher local dimensions ($q > 2$). We identify the existence of ”dual-
unitary” points where the model's space-time duality allows for exact analytical solutions. Our analysis reveals that while a few unique dual-
unitary points exist analytically for systems with local dimensions $q=3$ and $q=4$, such points do not exist for $q \ge 5$ due to the lack of a unique kicking strength that satisfies the required
matrix element conditions. Utilizing the transfer
matrix method and a replica trick specifically adapted for higher dimensions, we derive exact expressions for the growth of
entanglement entropy in the $q=3$ (kicked Potts-type) model starting from a class of solvable initial states. Our results demonstrate that at the dual-
unitary point, both Rényi and von Neumann
entanglement entropies grow linearly with time until reaching a maximum value determined by the subsystem size.
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Strongly Correlated Electrons
Robust spin pseudogap and spin-charge separation in the $\sigma t$-$J$ model
Zheng-Yuan Yue, Jia-Xin Zhang and Zheng-Cheng Gu
The $\sigma t$-$J$ model, obtained from the usual $t$-$J$ model by flipping the sign of the
spin-down hopping term, has been proposed to eliminate the strong interference between doped holes and the
spin background, known as the phase string effect. In this work, we investigate the finite-temperature properties of the $\sigma t$-$J$ model using infinite projected entangled-pair state (iPEPS)
algorithms, in comparison with the $t$-$J$ model and its easy-plane variants. We show that these models share similar
spin-pseudogap thermodynamics, with a maximum in the
spin susceptibility at $T^* \sim J$ and a broad specific-heat peak. Tensor network renormalization (TNR) further provides strong evidences for a Berezinskii-Kosterlitz-Thouless (BKT) transition in the
spin sector of the $\sigma t$-$J$ model at a lower temperature $T_\text{BKT} < T^*$ due to its reduced $\mathrm{U}(1)$
spin-rotation
symmetry. Crucially, in contrast to the $t$-$J$ model and to its easy-plane variants that also exhibit BKT transitions, these signatures remain robust upon doping: the doped holes preserve and even enhance the
antiferromagnetic correlations in the $xy$
spin plane, leading to a weak doping dependence of both $T^*$ and $T_\text{BKT}$. Finally, we develop a slave-
fermion mean-field theory for the $\sigma t$-$J$ model, whose projective
symmetry group (PSG) is selected based on numerically determined hopping and pairing correlations, and show that it explains the robust
spin pseudogap upon doping.
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Strongly Correlated Electrons
Uniaxial stress effects on magnetic and electric properties of the ground state in a centrosymmetric magnetic skyrmion host Gd$_2$PdSi$_3$
Hiraku Saito, Naoki Kobayashi, Takuro Kawasaki et al. (+5 more)
We investigate effects of uniaxial stress to
magnetic orders and electrical resistivity of the centrosymmetric
magnetic skyrmion compound Gd$_2$PdSi$_3$, which has a hexagonal
crystal structure composed of triangular
lattice layers of
magnetic Gd$^{3+}$ ions. This compound is known to exhibit the triple-$q$
magnetic skyrmion
lattice phase with a
giant topological
Hall effect in the first field induced phase [T. Kurumaji $\textit{et al}$. Science $\textbf{365}$, 914-918 (2019)]. In contrast to the established picture of the field-induced phase, the ground state of this system still remains to be studied. Although previous studies reported the existence of the incommensurate
magnetic modulations described by a
magnetic modulation wave vector ${\bf q}=(q,0,0)$ where $q\sim 0.14$ and its equivalents, it is still unclear whether the
magnetic structure is a single-$q$ structure or a multiple-$q$ structure. In the present study, we performed magnetization, resistivity and
neutron diffraction measurements with a compressive uniaxial stress applied perpendicular to the $c$ axis. The observed data revealed that the system did not exhibit anisotropic
magnetic and electric properties expected from a single-$q$
magnetic order, suggesting that the
magnetic ground state of this system is a multi-$q$
magnetic order.
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All authors Hiraku Saito, Naoki Kobayashi, Takuro Kawasaki, Tatsuya Nakamura, Akiko Kikkawa, Yasujiro Taguchi, Yoshinori Tokura, Taro Nakajima
Materials Science
Preserved metallicity and tunable magnetism in Zr-based Janus MXenes
S. Özcan and B. Biel
Janus MXenes provide a chemically asymmetric platform to tailor the properties of two-dimensional transition metal carbides. Here, we present a systematic first-principles study of the structural, electronic, mechanical, and
magnetic properties of Janus ZrMCX2 MXenes (M = Cr, Hf, Nb, Sc, Ti; X = F, Cl, S). All compositions exhibit negative formation energies and satisfy the Born stability criteria, supporting the energetic and mechanical stability of the Janus structures. In contrast to the metal-tosemiconductor transitions frequently reported for functionalized MXenes, we find that the metallic character is preserved in nearly all ZrMCX2 systems, despite the strong chemical asymmetry introduced by the Janus configuration. Surface functionalization nevertheless plays a key role in modulating the electronic density near the
Fermi level and strongly influences the
magnetic and mechanical responses. Several compounds exhibit
ferromagnetic or
antiferromagnetic ground states, three display halfmetallicity, and sizable
magnetic anisotropy energies are obtained, with Neel temperatures exceeding room temperature in selected cases. Functionalization also enhances the elastic stiffness of the Janus structures. These results demonstrate that chemical asymmetry and surface termination provide effective control over
magnetic and mechanical properties while maintaining a robust metallic framework, identifying Zr-based Janus MXenes as promising model systems for metallic and spindependent two-dimensional materials.
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Materials Science
A spin-bond theory unifying non-relativistic spin splitting and emergent spin-orbit textures
S. Allende and R. M. Otxoa
Magnetic order with vanishing net magnetization can produce non-relativistic
spin-split bands, broadly categorized into even-parity altermagnets and odd-parity \(p\)-wave magnets. Here, we introduce a
spin-bond theory that unifies these seemingly distinct phenomena into a single algebraic framework. We demonstrate that non-relativistic
spin textures are fundamentally governed by two components of the electronic bond:
unitary spin phases and Hermitian
spin amplitudes. The
unitary sector generates odd-parity p-wave and emergent
spin-orbit-like textures, while the Hermitian sector generates even-parity
spin fields, including the uniform \(\Gamma\)-split and bond-structured altermagnetic limits. Beyond unifying known phases, our theory uncovers a mixed non-commuting regime that emerges when the
unitary and Hermitian sectors fail to commute, revealing an underlying non-commuting
spin-bond structure. This regime generates a non-coplanar
spin texture characterized by an even-in-momentum transverse
spin polarization, providing a direct spectroscopic fingerprint for
spin- and angle-resolved photoemission spectroscopy. Furthermore, we establish that this synthetic
spin-orbit coupling can be dynamically tuned by geometrically controlling the non-commutation of the bond sectors. By providing a microscopic foundation for such tuning, our theory paves the way for advanced applications, including field-free
spin qubits.
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Mesoscale and Nanoscale Physics
Symmetry Breaking by Interfacial Dead Layers: Observation of Forbidden Self-Induced Spin-Orbit Torque in Symmetric Ferromagnets
Athira Ravindran K, Raghvendra Posti, Manish Kumar Mohanta et al. (+8 more)
Conventionally,
spin-orbit torques (SOTs) in ferromagnets require heavy-metal layers or engineered structural asymmetry to break inversion
symmetry. In this work, we report the observation of robust, self-generated SOTs in a nominally symmetric, heavy-metal-free MgO/NiFe/MgO trilayer - a geometry where such torques are theoretically forbidden. By combining harmonic
Hall measurements with SQUID magnetometry and X-ray photoelectron spectroscopy, we identify the
symmetry-breaking origin: a 1.8 nm
magnetic dead layer at the bottom interface. Crucially, we demonstrate a quantitative agreement between our data and the drift-
diffusion theory predicted by Kim and Lee, yielding a theoretically extracted dead-layer thickness (1.2 nm) which matches structural characterization. Furthermore, density-functional calculations confirm that NiFe possesses sufficient intrinsic
spin Hall conductivity to support the observed
spin currents. These results reframe the parasitic dead layer as a functional spintronic component, establishing a universal, all-
ferromagnetic route to SOTs in standard
magnetic heterostructures.
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All authors Athira Ravindran K, Raghvendra Posti, Manish Kumar Mohanta, Abhishek Kumar, Damanpreet Kaur, Alberto Anadón, Sebastien Petit-Watelot, Juan-Carlos Rojas-Sánchez, Michel Hehn, Puru Jena, Debangsu Roy