Strongly Correlated Electrons
Kibble-Zurek Dynamics in Two-dimensional Frustrated Systems with a Neural Foundation-state Subspace Method
Linda Mauron, Luciano Loris Viteritti, Zakari Denis et al. (+2 more)
Universal scaling generated when a strongly interacting
quantum many-body system is driven across a continuous phase transition provides a dynamical probe of
equilibrium criticality. Accessing this regime numerically in two dimensions is challenging because it requires accurate real-time
evolution of correlated many-body states over many system sizes and driving rates. We introduce a Neural Foundation-state Subspace (NFS) method for near-adiabatic dynamics. A foundation neural-network
quantum state represents the ground-state
manifold along the driving path, and a small fidelity-selected subset defines a fixed variational subspace. The many-body Schrödinger equation then reduces to the
evolution of a few linear coefficients, with projected operators reusable across ramp times. We validate the method on the two-dimensional transverse-field Ising model, recovering the expected Kibble-Zurek scaling and critical exponents in quantitative agreement with ground-state
quantum Monte Carlo estimates. Applied to the frustrated square-
lattice $J_1$-$J_2$ Heisenberg model up to $16 \times 16$ clusters, our approach provides strong numerical evidence of Kibble-Zurek mechanism across the Néel-to-
spin-
liquid transition at $J_2/J_1=0.49$, yielding ${\nu=1.23(15)}$ and ${\eta=0.409(19)}$ at fixed $z=1$, consistent with static estimates and supporting the proposed continuous critical behavior.
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All authors Linda Mauron, Luciano Loris Viteritti, Zakari Denis, Riccardo Rende, Giuseppe Carleo
Strongly Correlated Electrons · Cross-listed from cond-mat.mtrl-sci
Structural tuning of reduced exciton mass in layered HOIP compounds: Causation vs. correlation
Isaac R. Burkholder, Cindy Y. Wong, André Schleife et al. (+3 more)
Reduced
exciton mass ($\mu$) was recently reported to correlate strongly with a framework distortion in a series of nine single-layer (2D) metal-halide perovskite (HOIP) compounds. Specifically, $\mu$ was observed to increase in tandem with an alternating PbI4 octahedral tilt about an in-plane axis. In this work, we use group representation theory to decompose the observed framework distortions into displacive
symmetry modes of a common high-
symmetry parent framework. We find that all nine distorted frameworks involve linear combinations of the same six
symmetry modes, which have been reported to contribute to the framework distortions of a wide range of HOIP compounds. We show that these modes have highly correlated impacts on the band structure. To differentiate causation from correlation, we vary the amplitude of each mode independently and use density-functional theory to determine the resulting electronic band structures, from which $\mu$ is extracted. We find that bond-transverse displacements of the equatorial halide atoms increase $\mu$, while bond-transverse displacements of the apical halide atoms decrease it. Bond-axis displacements appear to have little or no effect on $\mu$. Our results demonstrate three new structure-property relationships, revealing a promising new avenue for
exciton engineering in layered perovskite materials.
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All authors Isaac R. Burkholder, Cindy Y. Wong, André Schleife, Kameron R. Hansen, John S. Colton, Branton J. Campbell
Strongly Correlated Electrons
Layer Architecture Shapes Electronic, Magnetic, and Lattice Interactions in Ruddlesden-Popper Nickelates
W. He, X. Guo, X. Luo et al. (+18 more)
The discovery of superconductivity in Ruddlesden-Popper nickelates has raised a central question: how does layer architecture shape the electronic,
magnetic, and
lattice interactions relevant to pairing? Here, we report a detailed comparative study of the two polymorphs of La3Ni2O7–the alternating monolayer-trilayer (LNO-1313) and bilayer (LNO-2222) structures–and the related trilayer compound La4Ni3O10, using both Ni L3- and O K-edge RIXS. We find that LNO-1313 and La4Ni3O10 share strikingly similar electronic,
magnetic, and
lattice excitations, whereas bilayer LNO-2222 exhibits distinct features. Compared to LNO-2222, LNO-1313 and La4Ni3O10 have weaker orbital polarization, enhanced 3d8L character, a reduced out-of-plane
magnetic-exchange scale, and stronger EPC. Within an effective local-moment framework, an entangled-dimer scenario provides a natural description of the
spin excitations generated by strong antiferromagnetic interlayer coupling. Its advantage over conventional
spin-wave theory is clearest in bilayer LNO-2222, where the interlayer coupling dominates the intralayer interactions. These findings provide critical experimental constraints for future theoretical models for the low-energy physics relevant to superconductivity in these layered nickelates.
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All authors W. He, X. Guo, X. Luo, J. Thomas, J. Sears, Sophia F. R. TenHuisen, Ziqiang Guan, Xinglong Chen, D. A. Dahlbom, B. Zager, J. Pelliciari, Yi-Feng Zhao, H. LaBollita, Hong Zheng, M. K. Lajer, J. F. Mitchell, V. Bisogni, A. S. Botana, M. Mitrano, S. Johnston, M. P. M. Dean
Strongly Correlated Electrons · Cross-listed from cond-mat.stat-mech
Fukui-Kawakami chains: spectrum and hidden $\mathfrak{gl}(1|1)$-symmetry
Rob Klabbers and Antoine Lefebvre
Fukui and Kawakami showed that the trigonometric Haldane–Shastry (HS)
spin chain can be deformed by introducing twisted boundary conditions. In this work we revisit the resulting twisted HS chains, which we call Fukui–Kawakami (FK) chains. We analyse their spectra in dependence of the twist parameter, utilising a direct connection with the (untwisted) HS chain. This allows us to explain why part of the spectrum can be described by Fukui and Kawakami's twisted Bethe equations, and can be constructed from Yangian highest weight states. These states can be labelled by combinatorial data called `motifs', as in the HS chain, which cover some of the (deformed) descendants. We furthermore show that there are other descendants which do not follow from these Bethe equations, but whose energy can be described as a sum of two single-particle energies, suggesting additional hidden
symmetries. We then focus on the special case of antiperiodic boundary conditions, and show that this chain coincides with the `minimally polarised' long-range model recently introduced by Basu-Mallick, Finkel, and González-López. Remarkably, this connection implies that the antiperiodic chain has a hidden $\mathfrak{gl}(1|1)$-
symmetry, which we use to relate the HS motifs to their `supersymmetric' $\mathfrak{gl}(1|1)$ counterparts.
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Strongly Correlated Electrons
Dual Charge-Density-Waves in Two-dimensional DyTe3 and Their Distinct Impacts on Magneto-Transport Properties
Shuvankar Gupta, Yasemin Ozbek, Olajumoke Oluwatobiloba Emmanuel et al. (+4 more)
Charge-density-waves (CDWs) are macroscopic
quantum states defined by periodic modulations in electronic charge density coupled with
lattice distortions. Despite significant research efforts, the
evolution of electromagnetic transport properties in the presence of CDWs remains largely unexplored. Here, we report the effects of two orthogonal CDWs (CDW1 and CDW2) coexisting at low-temperature in DyTe3 on its electronic transport properties. Importantly, we find that while no clear magnetotransport anomaly is resolved across CDW1 transition under the present experimental conditions, the emergence of CDW2 drives a drastic enhancement in magnetoresistance and a multiband-governed nonlinear Hall response. These results demonstrate that CDW1 and CDW2 in DyTe3 are fundamentally different and impact its electronic transport in qualitatively distinct ways, establishing DyTe3 as a model system for understanding the transport consequences of multiple CDWs in quasi-two-dimensional materials.
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All authors Shuvankar Gupta, Yasemin Ozbek, Olajumoke Oluwatobiloba Emmanuel, Maya Bostock, Johnathan Kowalski, Pengpeng Zhang, Xianglin Ke
Strongly Correlated Electrons · Cross-listed from cond-mat.mes-hall
The influence of quantum geometry on the phase boundary and collective excitations of electron liquids and crystals
Paul Froese, Mark R. Hirsbrunner and Yong Baek Kim
Recent experiments on multilayer
graphene systems have reinvigorated the study of electron crystallization, now with the inclusion of
quantum geometry. In this work, we apply time-dependent Hartree-Fock (TDHF) to the $\lambda$-jellium model to analyze the impact that
quantum geometry has on the electronic
liquid–
crystal phase diagram and how it modifies the collective modes and responses of the
liquid and
crystal phases. In agreement with recent results utilizing neural
quantum states, we find that
quantum geometry favours electron crystallization, shifting the transition to higher densities. We also study the instabilities revealed by TDHF in the Fermi
liquid ground state at low densities, providing insight into the fluctuations driving the crystallization transition. We further find that
quantum geometry reduces the dispersion of the plasmon mode and suppresses Friedel oscillations deep in the
liquid phase. Resolving the density response in terms of individual orbitals, we find that this suppression is caused by spectral weight transfer to an out-of-phase inter-orbital mode. Finally, we show that an analogous mode that emerges in the
crystal phase corresponds to the breathing mode of an emergent real-space pseudospin skyrmion
lattice.
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Strongly Correlated Electrons
Exact quantum spin liquids with topological order on maple-leaf and trellis lattices
Li Ern Chern, Roderich Moessner and Claudio Castelnovo
We construct
spin models with bond-dependent anisotropic interactions on the penta-coordinated maple-leaf and trellis
lattices, which yield exact $\mathbb{Z}_2$
quantum spin liquids akin to the Kitaev honeycomb model. We characterize the resulting ground states by their flux sectors, Chern numbers, and topological excitations. Using replica exchange
quantum Monte Carlo simulations, we find that the gauge fluxes are ordered at sufficiently low temperatures such that every unit triangle has $\pm \pi/2$-flux, where the sign is uniform across the system, and every unit hexagon (square) has $0$-flux ($\pi$-flux) within the parameter space of interest. We map out the topological phase diagram for each model, which reveals parameter regimes hosting $\mathbb{Z}_2$ and Ising topological orders, and we derive an analytical expression for the mass term of the Majorana
fermions, the vanishing of which indicates a transition between these phases. We further establish the correspondence between individual
vortices (i.e., flux excitations) and two species of anyons in the dimer limit, overcoming the obstacle faced by degenerate perturbation theory in treating odd-length elementary plaquettes. Interestingly, we find that two dimer limits of the maple-leaf model with distinct assignments of anyon species can be smoothly connected to each other in the
vortex-free sector, but they are separated by
fermion-gap-closing transitions in certain two-
vortex sectors.
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Strongly Correlated Electrons · Cross-listed from quant-ph
Strong-Drive Floquet Engineering of Interacting Qudits: From Finite-Duration Controls to Emergent Symmetry
Ryan Scott and V. W. Scarola
Floquet driving uses periodic controls to tailor the behavior of
quantum systems, with applications in
quantum analogue simulation, sensing, and the protection of
quantum information. Most approaches are designed using idealized, instantaneous pulses, even though experiments necessarily use pulses with finite duration and shape. This mismatch becomes especially challenging for interacting $d$-level systems, or qudits, because the number of possible controls grows rapidly with the number of levels. We develop a strong-drive Floquet theory that incorporates experimentally realizable pulse waveforms directly into the design of the effective interactions. The pulse duration, amplitude, and shape therefore become useful control parameters rather than sources of error. We show that systems with more than two levels offer capabilities unavailable in
qubit systems: finite-duration driving can create new interactions that are absent from the original system and can substantially change its
symmetries. We demonstrate these capabilities for interacting three-level systems. A single pulse transforms a diagonal interaction into a
quantum spin-1 model dominated by nematic interactions, while pulse protocols motivated by trapped ultracold polar molecules produce models with enlarged $SU(2)\times U(1)$ and $SU(3)$
symmetries. Numerical tests of both short-time
evolution and many-body dynamics confirm the accuracy of the resulting description. Our results provide a scalable analytical framework for designing finite-duration controls in interacting qudit platforms.
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Strongly Correlated Electrons · Cross-listed from hep-th
Eye-opening bounds on cusps
Ryan A. Lanzetta, Ian Moult and Yifan Wang
We derive new nonperturbative inequalities on the cusp anomalous dimensions of conformal line defects. We impose reflection positivity, locality, and conformal invariance on a pair of cusps forming an “eye” geometry, deriving a novel condition on the cusp anomalous dimension which we refer to as conformal concavity. The resulting constraint is much stronger than the known angular concavity, and our derivation applies also to cusps involving distinct line defects. Remarkably, it directly links the smooth and fusion limits, yielding bounds on defect-changing operator dimensions, Casimir energies, and subleading fusion data. We thus uncover a new quantitative bridge between aspects of the local operator data and the fusion rules of line operators in conformal field theories.
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Strongly Correlated Electrons
Donghae Seo, Taegon Lee and Gil Young Cho
Anyon superconductivity arises from the condensation of mobile anyons rather than from a conventional Cooper instability, yet a systematic wavefunction description remains lacking. We develop a hierarchy-wavefunction construction for superconducting states derived from parent topological orders and identify their off-diagonal long-range order, condensate charge, chiral central charge, and residual topological order through the
plasma analogy and topological field theories. We construct Abelian and non-Abelian examples descending from the semion state, a $\nu=2/3$ hierarchy state, the $\nu=1/3$ Laughlin state, $\nu=1$ integer
quantum Hall state, and Pfaffian state. Remarkably, for the semion case, the superconducting many-semion wavefunction is equivalent to a state of fermionized anyons filling two effective Landau levels, recovering Laughlin's original construction of semion
superconductor. Finally, we show that hierarchy wavefunctions emerge naturally in the dilute, long-distance limit of the anyon-
Hilbert-space formulation, which applies to ideal Chern bands and moiré bands of twisted bilayer MoTe$_2$. Our results establish a unified wavefunction-level framework linking anyon condensation, superconducting order, and topological field theory.
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Strongly Correlated Electrons · Cross-listed from cond-mat.supr-con
A Superconducting Peierls Instability
Pramodh Senarath Yapa, Joseph Maciejko, Frank Marsiglio et al. (+1 more)
The Peierls instability is a foundational mechanism in condensed matter physics, showing how the electron–
phonon interaction can transform a simple metal into an insulating state with a new
lattice periodicity. In a one-dimensional (1D) metal the Peierls instability follows from the enhanced electronic response at wavevector $Q=2k_F$ (connecting the Fermi points) producing a Kohn anomaly: a softening of the
phonon mode at the same wavevector. Condensation of this mode then generates the tell-tale Peierls periodic
lattice distortion and charge-density wave (CDW) that gaps the electronic spectrum. Here we show an analogous instability at the edge of a two-dimensional (2D)
superconductor, where a dispersing Andreev bound state (ABS) hosts Bogoliubov Fermi points at $\pm k_c$. The enhanced quasiparticle response at the connecting wavevector $Q=2k_c$ couples directly to pairing-fluctuations and produces a superconducting Kohn anomaly: a softening of a pairing mode at the same wavevector. Condensation of this mode then generates an edge pair-density wave (PDW) that gaps the ABS. We refer to this as a superconducting Peierls instability and identify the boundary quasiparticle structure that enables it. As a concrete realization, we consider a square-
lattice extended Hubbard model whose mixed-
symmetry $s+d+ip$ state hosts a dispersing ABS with zero-energy crossings at finite edge momenta. Using self-consistent Bogoliubov–de Gennes (BdG) calculations we show that the order parameter develops an edge PDW, with the wavevector set by the superconducting Kohn anomaly, that gaps the ABS crossings. Our results identify a novel mechanism for spontaneous translation-
symmetry breaking in a
superconductor. As this superconducting Peierls mechanism does not require an extensive zero-energy flat band or topologically protected edge states, it may apply broadly to unconventional
superconductors.
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All authors Pramodh Senarath Yapa, Joseph Maciejko, Frank Marsiglio, Annica M. Black-Schaffer
Strongly Correlated Electrons
Non-uniform quantum geometry stabilizes generalized Wigner crystals
Nicolás Morales-Durán, Tobias M. R. Wolf, Jingtian Shi et al. (+3 more)
Moiré materials host fractional Chern
insulators and electron
crystals in close proximity, but the mechanism selecting between them remains an open question. We address this competition in Chern bands with ideal but momentum-dependent
quantum geometry – Aharonov-Casher bands. We present an ansatz wave function for generalized Wigner
crystals and, by comparing its energy to that of the competing Laughlin-like state, map out the phase diagram at filling fraction $\nu=1/m$ as a function of the degree of
geometric non-uniformity. Our work identifies
quantum geometry-controlled zero point fluctuations of the charge density of the generalized Wigner
crystal as the mechanism controlling its relative stability, implying a kind of
quantum Lindemann criterion for the
crystal-
liquid phase boundary.
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All authors Nicolás Morales-Durán, Tobias M. R. Wolf, Jingtian Shi, Tomohiro Soejima, Andrew J. Millis, Jennifer Cano
Strongly Correlated Electrons
HyperDet Wavefunction: A Phase-Agnostic Ansatz for Strongly Correlated Systems
Xiaodong Hu, Guan-Lin Lin, Ying Ran et al. (+1 more)
Competing phases of strongly correlated systems are often described by trial wavefunctions built on phase-specific assumptions. We propose the hyperdeterminant (HyperDet) wavefunction as a phase-agnostic ansatz for both bosonic and fermionic
quantum many-body systems exhibiting spontaneous
symmetry-breaking, fractionalization, and/or topological order. The HyperDet structure emerges by fusing auxiliary fermionic parton Slater determinants into physical orbitals through a learnable \emph{fusion tensor $\mathcal F$}. Optimized using variational Monte Carlo, a single HyperDet architecture achieves overlaps exceeding $99.9\%$ with exact-diagonalization ground states for nearly all sampled parameters across fractional Chern
insulator (FCI) phases and their neighboring competing phases in both bosonic and fermionic models. Beyond its variational expressiveness, the optimized fusion tensor also provides rich interpretability. We show that, (i) the singular-value spectra of the bipartite fusion
matrix can be used to track phase transitions; (ii) the reconstructed Bott indices reproduce the parton Chern numbers expected for the FCI states without parton-
Hamiltonian input; and (iii) faithful lifts of physical translations to the parton degrees of freedom recover the expected translation fractionalization in the bosonic FCI without projective
symmetry class assignment. These results establish HyperDet wavefunction as a promising framework for both variational ground-state searches and phase-diagram explorations across strongly correlated phases, and for providing theoretical insights by connecting the optimized wavefunction with parton microscopics and field-theory descriptions.
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All authors Xiaodong Hu, Guan-Lin Lin, Ying Ran, Di Xiao
Strongly Correlated Electrons · Cross-listed from hep-th
Cutting corners: exciting and magical bounds from the cusp bootstrap
Ryan A. Lanzetta, Ian Moult and Yifan Wang
An illuminating probe of the dynamics of a line defect is the global geometry of its worldline. For a conformal line defect in a conformal field theory, sharp corners in the worldline, i.e. cusps, host dynamical degrees of freedom characterized in part by a spectrum of scaling dimensions, called cusp anomalous dimensions. We present various general bounds on cusp anomalous dimensions following from unitarity and cutting-and-gluing consistency of different defect geometries. We first establish, for cusps involving conjugate defects, that level crossings upon varying the cusp angle are forbidden between the lightest singlet cusp and any non-singlet cusp, proving that singlet cusps are the lightest. Then, we study line defects arranged in a rectangular geometry, which are subject to bootstrap constraints reminiscent of the spinless modular bootstrap. We find an analytic “magic" functional that produces an optimal and universal lower bound on the dimension of a right angle bare cusp in terms of the universal defect Casimir energy between the corresponding defect and its conjugate in flat space.
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Strongly Correlated Electrons · Cross-listed from quant-ph
Discrete time crystals in disordered anisotropic Heisenberg chains
Francesco Formicola, Grazia Di Bello, Antonio De Candia et al. (+2 more)
A discrete time
crystal is an out-of-
equilibrium phase of matter characterized by the spontaneous breaking of discrete time-translation
symmetry. Using extensive numerical simulations based on
matrix-product-state methods, we provide evidence for discrete time-crystalline behavior in strongly disordered
spin chains with Heisenberg interactions, including the isotropic point, subject to periodic driving. Starting from a many-body localized regime, we observe that rotations induced by delta kicks produce a pronounced subharmonic response at half the drive frequency in
spin observables. We investigate the stability of this response against rotation-angle errors through
entanglement entropy,
quantum Fisher information, short-range
spin correlations, and restricted-control ergotropy. Increasing the rotation error reveals an intermediate dynamical regime separating the time-crystalline and Floquet-localized responses. In this regime, most observables exhibit signatures of weakly correlated dynamics reminiscent of Anderson localization.
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All authors Francesco Formicola, Grazia Di Bello, Antonio De Candia, Giulio De Filippis, Carmine Antonio Perroni
Strongly Correlated Electrons · Cross-listed from hep-th
Cusped Defects: Cusp Operator Expansion, Conformal Properties and Bootstrap Applications
Lorenzo Bianchi, Andrea Cavaglià, A. David Gutiérrez et al. (+2 more)
We analyze general properties of cusped defect lines embedded in generic conformal field theories (CFTs). We prove that suitably defined cusp scaling operators transform like primary operators under general conformal transformations. We show that, via the cusp operator expansion (COE), defects of general shape can be expanded in a basis of cusped defects. These findings are checked and exemplified in the case of the localized
magnetic field defect. Finally, we derive analytic constraints on dynamical cusp data by making use of a crossing equation, and discuss possible numerical bootstrap applications of our results.
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All authors Lorenzo Bianchi, Andrea Cavaglià, A. David Gutiérrez, Stefanos R. Kousvos, Marco Meineri
Strongly Correlated Electrons
Evolution of electron spin resonance through a metallic quantum critical phase diagram
Marc Scheffler, Jörg Sichelschmidt, Conrad Clauss et al. (+6 more)
In the heavy-
fermion metal YbRh2Si2,
quantum criticality at a suppressed antiferromagnetic order is governed by the interplay of local
magnetic moments and itinerant conduction electrons. We demonstrate how this can be investigated by a new experimental approach that enables the observation of electron
spin resonance (ESR) across a broad range of frequencies and fields at very low temperatures. This allowed us to cover a large part of the phase diagram from the paramagnetic Fermi-
liquid phase to the phase with antiferromagnetic order and including the
quantum-critical regime. Both the ESR g-factor and the linewidth present distinct behaviors in these three regimes, providing further insight into the physics across a
quantum critical point. Notably, when cooling down at a field directly towards the
quantum critical point, both g-factor and linewidth continuously decrease. Furthermore, we observe a very good matching of the g-factor behavior upon field-tuning and temperature-tuning towards the
quantum-critical point. We analyze and discuss the results in the context of present theories on ESR in strongly correlated electron systems.
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All authors Marc Scheffler, Jörg Sichelschmidt, Conrad Clauss, Mojtaba Javaheri Rahim, Boris I. Kochelaev, Cornelius Krellner, Christoph Geibel, Frank Steglich, Martin Dressel
Strongly Correlated Electrons
Universal Driven Critical Dynamics of Entanglement Entropy
Chang-Yu Shen, Shuai Yin and Zi-Xiang Li
The Kibble-Zurek mechanism (KZM) and finite-time scaling (FTS) provide a foundational framework for driven critical dynamics, yet their predictive power has been largely confined to local observables. Here, we establish a universal finite-time scaling theory for the nonequilibrium dynamics of
quantum entanglement. Using unbiased
quantum Monte Carlo simulations, we investigate the corner
entanglement entropy of (2+1)-dimensional interacting Dirac
fermions driven from ordered phases toward a
quantum critical point. We find that the corner
entanglement accurately obeys a universal driven scaling governed by the driving rate and system size, persisting whether the initial ordered state is fully gapped or hosts gapless Goldstone modes. Crucially, this dynamical
entanglement exhibits a logarithmic dependence on the driving rate, from which the universal corner coefficient of the underlying conformal field theory can be robustly extracted far from
equilibrium. These results generalize the KZM from local observables to the intrinsic nonlocal
quantum information measures, offering a practical blueprint for characterizing
quantum criticality and
entanglement on programmable
quantum simulators.
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Strongly Correlated Electrons
Ground-State Phase Diagram, Higher-Winding Topology, and Lifshitz Criticality in an Anisotropic Four-Spin XX Chain
Mohammad Abbasi, Faraz Valeh and Saeed Mahdavifar
We investigate the
quantum critical and topological properties of a
spin-$1/2$ XX chain with anisotropic four-
spin cluster interactions in a transverse
magnetic field. The interplay of exchange anisotropy, cluster interactions, and the external field produces a rich phase diagram with multiple gapped topological phases and distinct
quantum critical boundaries. We identify several Lifshitz-type transitions arising from reconstructions of the low-energy Fermi-point structure, including an unconventional multicritical point where distinct critical branches intersect and the momentum-space
topology undergoes a singular reorganization. In the isotropic limit, a conventional Lifshitz transition emerges through the merging and annihilation of Fermi points, revealing distinct mechanisms of Fermi-point reconstruction within the same model. The gapped phases are characterized by quantized winding numbers $\nu=0,\pm1,-2,$ and $\pm3$, with the higher-winding phases induced by the extended cluster interactions. The $\nu=\pm3$ phases exhibit a richer topological structure than conventional short-range Kitaev-type chains and are separated from other sectors by field- and interaction-driven gap closings. These topological distinctions are further reflected in characteristic degeneracy patterns of the lowest levels of the bulk
entanglement spectrum. Our results demonstrate that anisotropic multispin interactions provide a versatile route to realizing higher-winding topological phases and unconventional multicriticality in one-dimensional
quantum systems.
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Strongly Correlated Electrons
Fermi-Point Topology Determines Emergent Conformal Criticality in Extended Quantum Spin Chains
Mohammad Abbasi and Saeed Mahdavifar
Quantum criticality in one-dimensional
quantum systems is characterized by emergent conformal field theories (CFTs), whose central charge counts independent gapless degrees of freedom. Establishing a microscopic connection between this universal conformal structure and the momentum-space
topology of the underlying quasiparticle spectrum remains challenging. Here, we uncover a direct correspondence between Fermi-point
topology, conformal criticality, and
quantum entanglement in an extended
quantum spin chain with competing cluster interactions, exchange anisotropy, and a transverse
magnetic field. We show that interaction- and field-driven Lifshitz transitions generate conformal critical phases with effective central charges $c_{\rm eff}=1/2$, $1$, $3/2$, $2$, and $3$, including a multicritical point where Ising and Luttinger-
liquid sectors coexist. Importantly, the central charge is not determined simply by the number of
lattice gap closings or Fermi points, but by the number and conformal content of independent low-energy continuum sectors after accounting for
lattice symmetries, reciprocal-
lattice identifications, and mode equivalences. Thus, Lifshitz transitions may leave the conformal anomaly unchanged or modify the central charge depending on whether spectral reconstruction generates new independent continuum sectors. Real- and momentum-space
entanglement spectra provide complementary microscopic signatures, revealing both the conformal content and momentum-space organization of critical modes. Our results establish a microscopic framework linking Fermi-point
topology to emergent CFTs and show how interaction-driven spectral reconstruction can generate higher-central-charge criticality and unconventional multicritical behavior.
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Strongly Correlated Electrons · Cross-listed from quant-ph
Fractalizing spacetime: Floquet codes with fractonic excitations that are immobile in space and time
Juliette Soule and Dominic J. Williamson
We generalize fractalization, a procedure for the construction of fracton models, from space to spacetime. We apply spacetime fractalization to construct fracton floquet codes with syndrome excitations that have limited mobility in space and time. This extends the notion of fracton order to intrinsically dynamical
quantum phases of matter that are inequivalent to static fracton phases. We find spacetime type-II fracton floquet codes which have no topological excitations that are mobile in space or time. These codes exhibit an extreme form of
quantum discrete time
crystal order with response periods that scale exponentially in their linear system sizes. In this context, the no-strings rule that characterizes type-II fractons leads to a superlinear scaling of the floquet code fault-distance with time, potentially lowering the time overhead required for
quantum error correction.
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Strongly Correlated Electrons
Hidden Magnetic Octupolar Order driven by Spin-Orbit coupling in KFeF$_3$
C. A. Crawford, C. I. Hiley, N. C. Bristowe et al. (+6 more)
Phase transitions are typically driven by
symmetry-breaking structural distortions that lift electronic degeneracies, yet in some cases, these transitions may be driven by a hidden order without conventional structural signatures. Here, we demonstrate that the 3$d$ perovskite, KFeF$_3$, hosts such a hidden instability. Using a combination of high-resolution powder diffraction, magnetometry,
symmetry-based analysis and first principles calculations, we reveal that while the 90 K cubic to rhombohedral transition arises from conventional magnetostriction accompanying antiferromagnetic order, a second transition at 40 K lowers the
symmetry to monoclinic without any detectable Jahn-Teller distortion or translational
symmetry-breaking.
Symmetry-based Landau analysis supports a hidden zone centered
magnetic octupole order parameter, whose improper coupling accounts for the weak ferromagnetism and pronounced
symmetry-breaking strain. Density functional calculations show that
spin-orbit coupling suppresses the competing Jahn-Teller instability, and thereby favors higher rank
magnetic multipolar degrees of freedom. These findings establish KFeF$_3$ as a model system in which the competing energy scales between
spin-orbit coupling and orbital degeneracy result in the emergence of hidden, multipolar order. We show that the control of such
magnetic, multipolar order could, in principle, provide a route to induce altermagnetism.
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All authors C. A. Crawford, C. I. Hiley, N. C. Bristowe, C. Stock, J. Gainza, C. Ritter, M. R. Lees, R. I. Walton, M. S. Senn
Strongly Correlated Electrons
Non-Resonant Impulsively Stimulated Raman Scattering by a Terahertz Field: a Case Study of 1T-TaS2
Haotian Zhang, Yuheng Guo, Zidu Yu et al. (+7 more)
Time-domain ultrafast and nonlinear terahertz spectroscopy techniques are recently applied to many condensed matter systems for investigating their collective excitations. In centrosymmetric systems, these collective modes are typically Raman-active and therefore do not couple directly to the terahertz electric field. The mechanism by which light-matter interaction realizes in these studies has not been explicitly discussed in detail. In this work, we perform terahertz pump - optical probe and terahertz third harmonic generation investigations on 1T-TaS2, a material exhibiting a rich charge-density-wave (CDW) phase diagram including the commensurate, nearly-commensurate and incommensurate CDW phases. The transition between these distinct states leaves a clear signature on the dynamical Raman response. We investigate how the Raman-active
phonons couple to a broadband monocycle terahertz field as well as a narrowband multicycle terahertz field. Our results indicate that a modified impulsively stimulated Raman scattering mechanism involving two-
photon absorption, also known as non-resonant Raman scattering, underlies the coherent excitation and observation of the
lattice modes. These results are relevant for future spectroscopy investigation and coherent control of collective modes using low-energy terahertz field as well as cavity electrodynamical dressing of solids.
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All authors Haotian Zhang, Yuheng Guo, Zidu Yu, Yongbo Lv, Yiting Wang, Liwen Feng, Jiaying Xu, Tianlong Xia, Xinbo Wang, Hao Chu
Strongly Correlated Electrons
Competing lattice structures induced by Sn substitution in CsV$_3$Sb$_5$
Anshu Kataria, Ilija K. Nikolov, Armando Consiglio et al. (+8 more)
Understanding the effect of chemical substitution on competing phases of kagome metals is crucial for disentangling the interplay between local structural distortions and electronic instabilities. In \cvs, Sn substitution strongly modifies the electronic phase diagram, yet the microscopic mechanism driving this remains unclear. Here, we combine $^{121}$Sb nuclear quadrupole resonance (NQR) measurements and density functional theory calculations to investigate the atomic-scale effects of Sn substitution in CsV$_3$Sb$_{5-x}$Sn$_x$. At low Sn concentrations, the observed satellite NQR peaks exhibit signatures of local structural distortion induced by Sn substitution, qualitatively consistent with our computational analysis. These impurity-induced features persist across the entire experimentally investigated doping range, up to $x$ = 0.65, and remain observable up to room temperature. For $x=1$, the fully doped idealized case, the estimated dynamical instabilities of the kagome
lattice suggest the stabilization of two nearly energy-degenerate
equilibrium structures characterized by V-trimers, distinguished by a zero- or $\pi$-phase shift between adjacent layers along the $c$-axis. Together, these results show that Sn substitution drives a complex interplay between local impurity-induced distortions and competing structural instabilities in vanadium-based kagome compounds.
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All authors Anshu Kataria, Ilija K. Nikolov, Armando Consiglio, Giuseppe Allodi, Ginevra Corsale, Andrea Capa Salinas, Stephen D. Wilson, Domenico Di Sante, Vesna F. Mitrović, Samuele Sanna, Pietro Bonfà
Strongly Correlated Electrons
Such stuff as magic is made on: compact operator algebra, stabilizer polytope and the structure of reduced density matrices in a Kitaev spin liquid
Snigdh Sabharwal, Nic Shannon and Paul Skrzypczyk
Quantum many-body systems exhibit rich and complex behaviour. Magic has recently emerged as a powerful new diagnostic for probing such systems, complementing other key features such as many-body
entanglement. Here, starting from an investigation of the onset of magic within subsystems of a larger many-body
quantum system, we show that intricate structures emerge which shed important light on the underlying many-body physics. Focusing on the Kitaev honeycomb model, we first identify the temperature below which local subsystems acquire magic. Remarkably, we find that the optimal magic witnesses active at the onset of magic reveal compact operator spaces that continue to capture the local thermal states throughout their subsequent
evolution. For the six-site hexagonal marginal, this connection can be made stronger: the same operator space emerges independently from the
symmetries of the local marginal and forms the
symmetry-resolved plaquette
algebra. When these
symmetries are realized exactly, the local state lies entirely within this
algebra and the reduced robustness of magic is equal to the full robustness of magic. The same reduced description can also be applied to other local
quantum resources, which we illustrate using genuine multipartite
entanglement. Furthermore, the operator spaces possess a rich algebraic structure in the form of finite-dimensional Euclidean Jordan
algebras, with a natural interpretation in terms of bond and bond-cycle operators. Our general methodology therefore show how the onset of local magic can reveal a compact, physically meaningful operator structure underlying the finite-temperature Kitaev
spin liquid, and opens up a new avenue towards reduced descriptions of
quantum resources in many-body systems.
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Strongly Correlated Electrons
Studying line defect at Deconfined Quantum Criticality via fuzzy sphere regularization
Shutao Liu, Shuai Yang, Jie Lou et al. (+1 more)
The interplay between bulk critical fluctuations and nontrivial
topology can enrich defect physics and give rise to novel defect universality classes. Understanding the fate of such defects therefore constitutes an important open problem. In this work, we studied a particularly simple setting: a (0+1)-dimensional pinning-field defect coupled to a (2+1)-dimensional deconfined
quantum critical bulk. Using the fuzzy-sphere regularization, we numerically investigated the defect operator spectrum and extracted several universal quantities characterizing the defect conformal fixed point, including the scaling dimensions of defect-changing(creating) operators and the defect \(g\)-function. These results establish the first numerical characterization of line-defect conformal data at deconfined
quantum criticality and may stimulate further investigations of defect critical phenomena in topological
quantum critical matter.
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All authors Shutao Liu, Shuai Yang, Jie Lou, Yan Chen
Strongly Correlated Electrons
Symmetry-breaking line defects embedded to a 3D $O(N)$ critical bulk
Shuai Yang, Liang-dong Hu, Yan Chen et al. (+1 more)
While spontaneous breaking of a discrete
symmetry in one-dimensional classical systems with short-range interactions is absent, it is expected that a line defect embedded in a bulk criticality exhibits a stable discrete
symmetry spontaneous breaking. Here, we investigate the behavior of a pinning-field line defect immersed in a 3D bulk that remains tuned to the $O(N)$ Wilson-Fisher critical point. Employing the fuzzy sphere technique, we provide convincing evidence of the existence of stable defect conformal fixed points, and we demonstrate their renormalization group stability by showing no relevant operator and less effective degrees of freedom than that at bulk fixed point via $g$-function. Moreover, we investigate the defect domain wall operator for various $N$, and we identify that it becomes irrelevance for $N\gtrsim 3$ but it is relevant for $N<3$.These evidence indicate that a one-dimensional defect coupled to a critical bulk cannot support a stable
symmetry spontaneously broken defect fixed point due to domain wall proliferation for $N<3$ Wilson-Fisher universality, while in the case of $N \gtrsim 3$ a
symmetry broken defect is possible.
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All authors Shuai Yang, Liang-dong Hu, Yan Chen, W. Zhu