Strongly Correlated Electrons · Cross-listed from cond-mat.mtrl-sci
Crystal growth, magnetic, and transport properties of the candidate altermagnet Cr$_{1/4}$NbS$_{2}$
Nashra Pistawala, Martin R. Lees, Geetha Balakrishnan et al. (+1 more)
Altermagnetism is a rapidly emerging paradigm in condensed matter magnetism, yet the number of experimentally confirmed altermagnetic candidates remains remarkably limited. Cr$_{1/4}$NbS$_2$ has long been theoretically proposed as a promising altermagnet, but there are no reports on experimental investigation of single
crystals. Here, we report the successful growth of high-quality single
crystals of Cr$_{1/4}$NbS$_2$ and present its structural, thermal,
magnetic, and transport properties. Single-
crystal X-ray diffraction provides detailed crystallographic information and confirms the hexagonal
crystal symmetry ($P6_3/mmc$), one of the criteria for altermagnetic behavior. Resistivity and heat capacity measurements unambiguously identify an antiferromagnetic Néel temperature of $T_N \sim 141$ K. Magnetotransport measurements reveal non-trivial features in the magnetoresistance and Hall response, indicative of
quantum diffusive transport phenomena. Cr$_{1/4}$NbS$_2$, synthesized here for the first time in single-crystalline form, therefore serves as an experimental platform for probing the rich spectrum of phenomena predicted for altermagnetic materials.
Read the full abstract ▾
All authors Nashra Pistawala, Martin R. Lees, Geetha Balakrishnan, Daniel A. Mayoh
Strongly Correlated Electrons · Cross-listed from quant-ph
Krylov Complexity and Quantum Many-body Scars in Non-Hermitian Kinetically Constrained Models
Arkaprava Sil, Rudraksh Kaushik, Souvik Kundu et al. (+2 more)
Thermalization in closed
quantum systems and its breakdown are central to understanding the emergence of statistical behavior in isolated many-body systems. Kinetic constraints can hinder thermalization by restricting the allowed dynamics and giving rise to non-ergodic behavior. While various aspects of ergodicity breaking in kinetically constrained models have been extensively studied in Hermitian systems, their behavior in non-Hermitian kinetically constrained models remains less explored. In particular, the inequivalence of left and right eigenstate ensembles in non-Hermitian systems raises the question of whether they exhibit qualitatively different dynamical and eigenstate properties. In this work, we study non-Hermitian generalizations of the paradigmatic PXP and PPXPP models, focusing on their Krylov complexity, eigenstate structure, and dynamics. By exploiting the Arnoldi's
algorithm, we find distinct behavior of Krylov complexity in the left and right eigenstate ensembles as non-Hermiticity is increased: in the right ensemble, it exhibits persistent oscillations with an increasing period, while in the left ensemble, it gradually saturates. The characteristic arch-shaped profile of the Arnoldi coefficients is also modified differently in the two ensembles, with a Hermitian-like arch re-emerging in the left ensemble at large non Hermiticity. Additionally, in the non-Hermitian PXP model, the right ensemble retains the characteristic scar structure, while the left ensemble develops additional non-scar eigenstates with anomalously low
entanglement and large overlap with the
vacuum state. These findings reveal that non-Hermiticity can affect Krylov dynamics and eigenstate structure differently in the left and right ensembles, demonstrating the need to treat them separately when characterizing non-Hermitian kinetically constrained systems.
Read the full abstract ▾
All authors Arkaprava Sil, Rudraksh Kaushik, Souvik Kundu, Prasant Mallik, Sudipto Singha Roy
Strongly Correlated Electrons
Quantum skyrmion molecule: two quantum skyrmions bound by coherent magnon exchange
Ricardo L. Silva
Quantum skyrmions in frustrated
spin-$1/2$ magnets are bound states of a few flipped
spins in a ferromagnetic background. Using exact diagonalization and density-
matrix renormalization group calculations for the $J_1$–$J_2$ triangular-
lattice model with easy-axis anisotropy $K$, we ask what happens when two such objects are brought together. The binding energy per flipped
spin of a single skyrmion has a minimum at $\Nf^{*}=7$ for $K=0.02$–$0.04$, and skyrmions smaller than $\Nf^{*}$ do not exist as pairs: at any distance they coalesce into a single larger object, and pinning wells cannot prevent it. Two skyrmions of natural size, by contrast, form a bound molecule without pinning or external field, with binding energy $U\simeq-0.007J_1$ at $K=0.03$–$0.04$ and an
equilibrium separation of $5.5$
lattice spacings that does not depend on $K$ or on the size of the simulation domain; at $K=0.02$, where the single skyrmion is itself marginally bound, the pair is unbound within our resolution. The two constituents keep their identity ($7+7$ flipped
spins) and are coupled by a coherent exchange of
magnons, visible as number fluctuations between the two halves of the domain in excess of those of two independent skyrmions and as in-plane
spin correlations between the two skyrmion walls that reach $0.16$ across the gap. These correlations follow the
vortex pattern of the two textures and lock their relative helicity, the
quantum counterpart of the helicity-dependent interaction of classical skyrmions. We discuss the molecule as a self-assembled two-
qubit element for skyrmion helicity
qubits in a single layer.
Read the full abstract ▾
Strongly Correlated Electrons
Phase-Coherent Spin and Lattice Modulations in a Y-type Hexaferrite
Oskar Stepančić, Annika Stellhorn, Emma Campillo et al. (+7 more)
Spin-driven multiferroics owe their electric polarization to
lattice distortions that follow the
magnetic order, yet in incommensurate magnets
symmetry normally forbids such a distortion at the fundamental
magnetic wavevector, and the distortions themselves are rarely observed. Here we use half-polarized
neutron scattering to show that the Y-type hexaferrite Ba$_{0.4}$Sr$_{1.6}$Mg$_2$Fe$_{12}$O$_{22}$ hosts, in its saturated high-field state, a
magnetic modulation and a longitudinal
lattice modulation at one and the same wavevector, locked in phase. The signature is a large nuclear-
magnetic interference asymmetry, $r$ ~ 0.8, of the same sign at the two conjugate satellites and persisting to 275 K. The zone contrast and the field dependence of the satellite indicate an internal, field-induced longitudinal distortion. The modulated state coexists with the transverse-conical magnetoelectric phase and outlives it, revealing a fundamental-wavevector
spin-
lattice coupling in a
magnetic field regime previously regarded as a simple ferrimagnet.
Read the full abstract ▾
All authors Oskar Stepančić, Annika Stellhorn, Emma Campillo, Kun Zhai, Niklas Ekström, A. Corani, D. Alba Venero, R. Cubitt, E. Blackburn, L. Shen
Strongly Correlated Electrons
Pairing from repulsive interactions in twisted WSe2 from functional renormalization
Hannes Braun, Dumitru Călugăru, Pietro M. Bonetti et al. (+9 more)
Motivated by the observation of superconductivity in twisted bilayer WSe$_2$ over an extended range of displacement fields, reaching from the correlated
insulator down to zero field, we analyze the correlated electron phases of this system at hole filling $\nu = -1$ and twist angle $3.65^\circ$ using Hartree–Fock, random phase approximation, and functional renormalization group calculations. We derive a continuum model with gate-screened Coulomb interaction from first principles and compare its instabilities to those of a realistic three-orbital Wannier model with a Hubbard interaction and an artificial single-orbital Hubbard model. In both cases, we find a superconducting instability of mixed $d$-wave singlet and $p$-wave triplet character, arising adjacent to inter-valley-coherent
spin-density-wave order in the phase diagram spanned by displacement field and interaction strength. Our additional analysis of the pairing mechanism points to inter-valley coherent
spin fluctuations as the pairing glue. The extent of the pairing regime and the associated critical temperatures depend on the model input, and we trace differences to the interaction range entering the projected interaction. Within the continuum model, the gate-screened Coulomb interaction yields pairing down to zero displacement field, bringing theory into agreement with experiment.
Read the full abstract ▾
All authors Hannes Braun, Dumitru Călugăru, Pietro M. Bonetti, Haoyu Hu, Yan Zhang, Yi Jiang, Quansheng Wu, Kin Fai Mak, Jie Shan, B. Andrei Bernevig, Michael M. Scherer, Laura Classen
Strongly Correlated Electrons · Cross-listed from quant-ph
Fermionic non-Gaussianity via computable measures and experimentally accessible bounds
Leela Ganesh Chandra Lakkaraju, Naga Dileep Varikuti and Philipp Hauke
Interacting
fermions owe both their non-trivial correlations and their computational power to their departure from Gaussianity. Yet, quantifying that departure geometrically faces two challenges: the Gaussian
manifold is non-convex, and perturbative treatments are confined to weak interactions. Here, we introduce a
geometric measure of fermionic non-Gaussianity, the fidelity distance of a target state to the
manifold of fermionic Gaussian states. We construct an iteration formalism to numerically access it, applicable also at strong coupling. Further, we prove a sharpened operator Jensen inequality, of interest in its own right. We use it to derive a witness that involves only two- and four-point fermionic correlators. Numerical
benchmarks on the one-dimensional Fermi–Hubbard model show that the quality of the witness improves with system size and, for strong coupling, is tighter than antiflatness. Our results open a scalable route to charting non-Gaussianity of strongly-interacting fermionic
quantum simulators.
Read the full abstract ▾
Strongly Correlated Electrons
Berry curvature from plane-wave mixing: A three-band model with emergent symmetries
Avi Vadali and Tomohiro Soejima
Two-dimensional materials can host topological phases stabilized either by an intrinsic moiré potential or topological crystallization. Crucial to the
topology of these phases is the interplay between the (self-consistently generated) potential and the spinor structure, which imbues the band-projected potential with momentum-dependence. Truncating this potential at linear-order in momentum, we obtain a three-band model that captures the low-energy band structure and Berry
curvature of such topological bands. We analytically find that the Berry
curvature strongly depends on momentum-dependence of the potential. Furthermore, we identify that the model can be tuned to have emergent
symmetries, including $U(1)$ and anti-
unitary symmetries. Emergent-
symmetry breaking perturbations drive the system to regimes hosting topological flat bands, quadratic band touchings, and multiple Dirac cones. We recover many of these features when studying an un-truncated model of a $\lambda$-jellium spinor inside of a periodic potential. Our results reveal a rich interplay of spinor structure and a potential in determining the
topology of the ground state.
Read the full abstract ▾
Strongly Correlated Electrons · Cross-listed from quant-ph
Entanglement Sudden Death in Gapped Ground States
Robert Ferydouni, Thomas Jackson and Samuel O. Scalet
Spatial sudden death of
entanglement refers to the disappearance of
quantum correlations between subsystems after a certain distance called the
entanglement length. Specifically, given a density
matrix $\rho_{ABC}$ on a tripartite system $ABC$ with $B$ spatially separating $A$ and $C$, the
entanglement length is the distance $\ell(A,C)$ after which the reduced density
matrix $\rho_{AC}$, given by tracing out the $B$ subsystem, is separable. We show in the case of gapped ground states in any dimension that the
entanglement length is finite on finite subsystems. Restricting to one-dimensional systems, we prove that normal
matrix product states have a finite
entanglement length independent of $A$ and $C$, and that a finite pure state with such uniform
entanglement length has a
matrix product state representation with bond dimension independent of $A$ and $C$. Consequently, in one dimension,
entanglement length distinguishes
matrix product states from all other pure states.
Read the full abstract ▾
Strongly Correlated Electrons
Honeycomb Crystal in a Mass-Asymmetric Electron-Hole Bilayer
Shengdu Chai, Wangqian Miao, Yuqiang Li et al. (+3 more)
A two-dimensional electron gas in a uniform neutralizing background forms a triangular Wigner
crystal at low density. In a strongly mass-asymmetric electron-hole bilayer, localized heavy holes instead provide a nonuniform positive background that supports an electron
crystal at densities two orders of magnitude higher than for a homogeneous electron gas in the same material. Here we show that correlated mobile electrons can overturn the preference for triangular order, stabilizing a honeycomb electron-hole
crystal. Using the powerful real-space neural-network variational Monte Carlo in the Born-Oppenheimer limit with fixed holes, we find that increasing the density drives a transition from a triangular electron-hole
crystal to a honeycomb
crystal, which eventually melts into itinerant electrons coexisting with the honeycomb or the triangular hole
lattice at fixed interlayer separation. Relative to triangular order, honeycomb order emerges when gains in electronic kinetic energy and electron-hole attraction outweigh its higher intralayer Coulomb repulsion, a threshold never reached in the rigid point-dipole model. Moreover, the honeycomb hole
lattice supports paramagnetic, antiferromagnetic, and stripe-ordered
spin states. Complex polarization indicates a metal-
insulator transition, while the states on the honeycomb hole
lattice are consistent with a stripe-ordered Dirac semimetal and paramagnetic or antiferromagnetic Mott
insulators via mapping to the half-filled Hubbard model. We further propose a BLG/hBN/WS$_2$-WSe$_2$
heterostructure as a platform for the predicted honeycomb
crystal, at an experimentally feasible density $n\sim10^{11}~\text{cm}^{-2}$.
Read the full abstract ▾
All authors Shengdu Chai, Wangqian Miao, Yuqiang Li, Lei Wang, Xi Dai, X.C. Xie
Strongly Correlated Electrons
Microscopic Theory of the Acoustic Faraday Effect in Spin-Orbit Coupled Magnets
Antoine Matar, Haoting Xu and Hae-Young Kee
The acoustic Faraday effect probes
phonon Hall viscosity through the rotation of transverse acoustic polarization, conventionally interpreted in terms of circular birefringence. We show that
magnetic order breaking rotational
symmetry generates anisotropic
phonon responses and elliptically polarized eigenmodes, so that Faraday rotation cannot be attributed to Hall viscosity alone. To elucidate their microscopic origin and consequences, we derive
spin-
phonon couplings from a generic $J$-$K$-$\Gamma$-$\Gamma'$ model with interlayer coupling, identifying transverse strain couplings for propagation along the $c$-axis arising from the interplay of Kitaev $(K)$ and $\Gamma$ interactions, along with strain-induced $g$-tensor contributions. Incorporating these couplings into our theory for the Kitaev
spin-
liquid candidate $\alpha$-RuCl$_3$, we find that
symmetry breaking modifies the Faraday response, revealing a Hall viscosity approximately twice the value inferred assuming rotational
symmetry. Our results establish a microscopic framework beyond circular birefringence, refining the connection between acoustic Faraday rotation and
phonon Hall viscosity in
symmetry-broken
spin-orbit-coupled magnets.
Read the full abstract ▾
Strongly Correlated Electrons
Emergent low-energy thermodynamics and universal $B/T$ scaling in $\alpha$-RuCl$_3$
A. Khansili, B. J. Ramshaw, A. Bangura et al. (+6 more)
Quantum spin liquids are exotic states of matter in which strongly interacting
spins remain disordered down to zero temperature and host fractionalized excitations. This has motivated an extensive search for their realization in materials. Among candidate systems, $\alpha$-RuCl$_3$ has drawn particular
attention as a platform for the
quantum spin liquid proposed by Kitaev, in which the low-energy excitations in applied
magnetic fields are interpreted as itinerant Majorana
fermions and local flux excitations. However, conflicting experimental signatures have cast doubt on whether a Kitaev
quantum spin liquid-like state is really the right starting point to interpret the low-energy states in $\alpha$-RuCl$_3$, motivating a closer look at the nature of these excitations. Here we report an extensive high field study of specific heat up to 35 T on $\alpha$-RuCl$_3$. We find that the low-energy thermodynamics exhibit universal $B/T$ scaling with a single effective energy scale proportional to the applied field as long as the
magnetic field is not close to the $c$-axis. This behavior persists continuously from the antiferromagnetic phase boundary to the highest fields, suggesting that the perturbative Kitaev limit, with its Majorana and flux excitations, may not be an appropriate starting point for describing the low-energy thermodynamics of $\alpha$-RuCl$_3$ for fields away from the $c$-axis.
Read the full abstract ▾
All authors A. Khansili, B. J. Ramshaw, A. Bangura, H.-Y. Kee, R. D. McDonald, F. Assaad, A. Rydh, A. Shekhter, K. A. Modic
Strongly Correlated Electrons · Cross-listed from cond-mat.supr-con
Microscopic Modeling of Interlayer Tunneling in Twisted Bilayer Cuprates
Siddhant Panda, Andreas Kreisel, Laura Fanfarillo et al. (+1 more)
The field of twistronics, recently extended to twisted bilayer cuprate systems, has generated considerable interest due to the prediction of $d+id'$ states close to a $45^\circ$ twist, as suggested by multiple experimental probes. Theoretical studies of these systems using a variety of models and many-body theoretical techniques have revealed multiple competing order parameters. The large variability in experimental results and theoretical predictions demands an accurate microscopic model for these systems, in particular a more realistic description of the interlayer tunneling. In this study, we fit the in-plane hopping and compute the interlayer tunneling amplitudes by calculating the orbital overlap between $d_{x^2-y^2}$ wave functions at each site of the twisted square-
lattice model. We observe sign-changing tunneling amplitudes, a strong twist-angle dependence of the direct tunneling term, and long-range tunneling amplitudes that often dominate over direct tunneling. We investigate the band structure, Fermi surfaces, and spectral functions in comparison with those obtained from the phenomenological model and find a substantial redistribution of spectral weight that modifies the competition between different superconducting ground states. We determine the phase diagram as a function of twist angle, filling, and direct tunneling strength, which is controlled by the $c$-axis distance between the monolayers, and observe a reduction in the region of time-reversal-
symmetry-breaking (TRSB) $d+id'$ states compared with the phenomenological model. Finally, we investigate the Josephson critical current across the phase diagram and find strongly suppressed critical currents close to a $45^\circ$ twist, consistent with experimental observations.
Read the full abstract ▾
All authors Siddhant Panda, Andreas Kreisel, Laura Fanfarillo, P. J. Hirschfeld
Strongly Correlated Electrons
Mutual information across the commensurate–incommensurate crossover and near the Kosterlitz–Thouless point of the spin-$\tfrac12$ $J_1$–$J_2$ Heisenberg chain
Wuttichai Pankeaw and Pruet Kalasuwan
What
quantum mutual information adds to conventional correlation functions is often unclear. We study the
spin-1/2 $J_1$-$J_2$ Heisenberg chain, using DMRG on infinite chains and periodic rings and an SU(2) decomposition of the mutual information into correlation channels. For singlet ground states the two-site mutual information is an exact function of the
spin correlator, so any additional content must come from blocks. In the dimerized phase, blocks resolve bond-energy correlations in the SU(2)-scalar channel without an independent asymptotic length: singlet and triplet correlation lengths agree to about 1%. The scalar channel dominates block mutual information at large distances in the commensurate regime up to $J_2/J_1=0.40$, but falls to a few percent beyond the disorder point, which coincides numerically with the Majumdar-Ghosh point $J_2/J_1=1/2$; the structure-factor peak splits only at the Lifshitz point $J_2/J_1=0.520622(2)$. On the gapless side we compare block mutual information on rings extrapolated to infinite size with the two-interval prediction of SU(2)$_1$ conformal field theory across the Kosterlitz-Thouless point $J_2/J_1=0.241167$. There, for block lengths $l\le6$, the correction decays as $l^{-p}$ with $p=1.96$-$2.07$, and any logarithmic term is at least 60 times smaller than in the Heisenberg chain. Expanding in the marginal coupling (from level spectroscopy) the first-order coefficient is consistent with $l^{-2}$ scaling and the second-order coefficient is positive for $x\le1/4$, suggesting that the mutual information relative to the field-theory value becomes stationary at the KT point for large blocks. The scalar-channel share approaches 1/4 at small cross ratio $x$, as expected from SO(4)
symmetry; under two stated assumptions its first-order response to the coupling is $(3/8)\ln x-5/8$ at small $x$, matched by the $l=4$ data within 1-3% at $x\le1/9$.
Read the full abstract ▾
Strongly Correlated Electrons · Cross-listed from hep-th
Out-of-time-order hydrodynamics and scrambling
Marta Bucca, Akash Jain, Márk Mezei et al. (+1 more)
Hydrodynamics as an effective field theory (EFT) has been immensely successful for predicting the behaviour of time-ordered correlation functions in the long-time, large-distance regime. In this paper, we analyse the predictions of hydrodynamics for scrambling as probed by out-of-time order correlators (OTOCs). To do so, we consider an all-derivative order generalisation of the Schwinger-Keldysh EFT of hydrodynamics extended to a four-fold time contour required to capture OTOCs. A crucial ingredient of the construction is a local SL(2,R)
symmetry, which has previously been suggested as a mechanism for scrambling. We also derive this exact EFT from the microscopic formulation of the maximally chaotic low-temperature limit of the SYK
lattice, thereby determining all transport coefficients for this model. As a novel application, we compute the OTOC of energy currents, find that its exponential growth saturates the chaos bound, and match it to expectations based on a shockwave (or scramblon) effective description. Our work shows that the universality of hydrodynamics degrees of freedom extends beyond traditional time-ordered correlators to more complex observables such as OTOCs.
Read the full abstract ▾
All authors Marta Bucca, Akash Jain, Márk Mezei, Alexey Milekhin
Strongly Correlated Electrons
Magnetic properties and excitation spectrum of the S = 1/2 three-legged spin ladder, LiMoOP2O7
Aly H Abdeldaim, Alexander A. Tsirlin, Jacques Ollivier et al. (+4 more)
We report a comprehensive experimental study including density functional theory calculations detailing the
magnetic ground state of the $S = 1/2$ Mo$^{5+}$ pyrophosphate, LiMoOP2O7, and its
magnetic excitations.
Neutron powder diffraction measurements confirm the $P2_1/n$ structural model which is comprised of a three-legged ladder of distorted Mo$^{5+}$ octahedra. Magnetometry and specific heat reveal a long-range
magnetic ordering transition at $T_\textrm{N} = 3.5$~K and a field-induced transition at $\mu_{0}$H$_\textrm{c}$ = 1 T. This zero-field long-range
magnetic order was determined to be a commensurate $\kappa = 0$ order with an ordered moment that is reduced from the full $S = 1/2$
magnetic moment by 30%. Through inelastic
neutron scattering measurements and density functional theory calculations, we define the minimal microscopic model and resolve the
spin Hamiltonian up to the seventh leading exchange parameter, resulting in a model with dominant antiferromagnetic leg interactions, weaker ferromagnetic rung interactions, and a significant interlayer ferromagnetic coupling.
Read the full abstract ▾
All authors Aly H Abdeldaim, Alexander A. Tsirlin, Jacques Ollivier, Clemens Ritter, Robin S. Perry, Lucy Clark, Gøran J. Nilsen
Strongly Correlated Electrons
Quantum Ising transition on the Cayley tree: boundary criticality, universality, and an effective Bethe line
Pietro Richelli and Natalia Chepiga
We investigate
quantum criticality in the transverse-field Ising model on finite Cayley trees and demonstrate that their extensive boundary fundamentally changes the nature of the
quantum phase transition compared with the infinite, boundary-free Bethe
lattice. Using tree tensor-network simulations for systems with up to $N=12286$ sites, we identify a boundary-driven continuous transition at $h_x^c\approx1.76$, distinct from the mean-field Bethe-
lattice transition at $h_x^c\approx2.23$. We characterize this transition through finite-size scaling of the magnetization and
magnetic susceptibility and extract a consistent set of critical exponents. By introducing next-nearest-neighbor interactions, we demonstrate the robustness of the extracted critical exponents, providing numerical argument for the Ising boundary universality class on the Cayley tree. Furthermore, we show that the physics of the boundary-free Bethe
lattice can be efficiently recovered on a finite Cayley tree by fine-tuning a local boundary field. The resulting effective Bethe line, whose existence is tied to the mean-field nature of the bulk transition, effectively screens the extensive boundary and restores both the critical point and the mean-field critical scaling of the infinite Bethe
lattice.
Read the full abstract ▾
Strongly Correlated Electrons
Destructive Interference of a Charge Density Wave in the Skyrmion Magnet GdRu2Si2
G. D. A. Wood, D. A. Mayoh, F. Orlandi et al. (+10 more)
In skyrmion magnets, charge density waves induce higher-order exchange interactions that can select multi-Q ground states. Using resonant X-ray scattering and
neutron diffraction, we measure temperature-dependent
spin-charge coupling in GdRu2Si2. A minimal Landau model with one critical exponent and two ordering temperatures reproduces all six observed order parameters.
Spin-density wave components of the multi-Q ground state drive charge ordering, but the onset of a
magnetic helix suppresses it via destructive interference.
Read the full abstract ▾
All authors G. D. A. Wood, D. A. Mayoh, F. Orlandi, A. Bombardi, D. D. Khalyavin, P. Manuel, S. H. Moody, P. D. Hatton, R. D. Johnson, T. W. Chamberlain, O. A. Petrenko, M. R. Lees, G. Balakrishnan
Strongly Correlated Electrons
Confinement-deconfinement transitions in the dimer-loop models on two-dimensional non-bipartite lattices
Jay Pandey, Souvik Kundu and Kedar Damle
Recent work [Kundu, Damle, Phys. Rev. X 15, 011018 (2025)] has demonstrated that a class of $S=1$ kagome
lattice antiferromagnets with competing anisotropies can exhibit unusual low-temperature behavior that is best described in terms of the statistical mechanics of an interesting interpolation between the fully-packed dimer model and the fully-packed loop model on the bipartite honeycomb
lattice. On this and other bipartite
lattices in two and three dimension, such fully-packed dimer-loop models generically have two distinct power-law correlated Coulomb phases, both of which admit a low-energy description in terms of a fluctuating divergence-free polarization vector field [Phys. Rev. X 15, 011018 (2025); arXiv:2510.11607]. The transition between these phases corresponds to a confinement transition for the $Z_2$ part of the corresponding $U(1)$ flux [Phys. Rev. X 15, 011018 (2025); arXiv:2510.11607]. Here we demonstrate that a variant of such a topological confinement transition can also exist in dimer-loop models on non-bipartite
lattices such as the kagome and triangular
lattices although the low-energy description does not feature any conserved $U(1)$ flux. In these non-bipartite dimer-loop models, both phases are short-range correlated
liquids, and the topological distinction between them is in terms of a $Z_2$-valued winding number instead of the flux of a divergence-free polarization field. In spite of this key difference, this transition appears to be in the same Ising universality class as the analogous transition of the bipartite dimer-loop models. These kagome and triangular
lattice dimer-loop models correspond respectively to the low-energy limit of a class of $S=1$ antiferromagnets with competing anisotropies on the ruby
lattice comprising a corner-sharing arrangement of fully-frustrated squares and a
lattice of corner-sharing fully-frustrated hexagons.
Read the full abstract ▾
Strongly Correlated Electrons
Topological Chiral Superconductivity from Doping Correlated Charge Transfer Insulator with Orbital Magnetism
Wen Sun, Yuan Yang, Shou-Shu Gong et al. (+1 more)
Topological chiral superconductivity has been extensively studied from the perspective of electronic structures in momentum space, while its emergence from real-space processes in strongly interacting systems remains largely unexplored. Here, we study a doped charge-transfer
insulator in a strongly repulsive spinless-
fermion model with three sublattices and $2\pi$ flux per unit
cell. Combining perturbative analysis, exact diagonalization, and density
matrix renormalization group simulations, we establish a topological superconducting ground state with $p+ip$
symmetry. In the large charge-transfer gap limit, chiral charge-transfer excitations generate a correlated-hopping process that provides a microscopic mechanism for electron pairing and its chiral structure. The chiral superconductivity persists into the smaller-gap regime, where chiral excitonic two-particle bound state can emerge. Our results establish a concrete real-space route to topological chiral superconductivity upon doping strongly interacting charge-transfer
insulators with orbital magnetism.
Read the full abstract ▾
All authors Wen Sun, Yuan Yang, Shou-Shu Gong, Wen Huang
Strongly Correlated Electrons · Cross-listed from cond-mat.mes-hall
Nontrivial topological properties from the cooperation of static perturbations and Floquet fields in type-II semi-Dirac semimetals
Wen-Hao Bian and Jing Wang
In this work, we present a comprehensive theoretical study for the topological and anomalous transport properties of type-II SDSMs under three scenarios, i.e., static
symmetry-breaking perturbations, periodic Floquet driving by two-frequency orthogonally polarized light (TFOPL), and their cooperative effects in the hybrid scenario. We first show that a static mass $m_z$ opens a bulk gap and drives the system into a Chern
insulator with Chern number $C^{\rm per}=\pm 2\,{\rm sgn}(m_z)$. In comparison, TFOPL alone only shifts the positions of Dirac points and cannot open a full gap. Nevertheless, it produces a Berry
curvature odd in the $x$-direction, yielding a finite Berry
curvature dipole (BCD) along $x$ proportional to the sine of the initial phase, while the $y$-component vanishes. The hybrid scenario, by contrast, exhibits a remarkably rich phenomenology. Specifically, its gap-closure criterion becomes cubic and thus admits up to three real roots when the effective parameter along the $x$-direction is negative, thereby producing multiple light-tunable gap-closing points and a series of topological phase transitions. In particular, the BCD exhibits a double-peak structure with strong enhancement near gap-closing
manifolds and synchronized sign reversal of the full vector under external tuning. We further analyze the anomalous Hall conductivity (AHC), anomalous Nernst conductivity (ANC), and anomalous thermal Hall conductivity (ATHC). The AHC and ATHC exhibit quantized plateaus that serve as signatures of Chern-
insulator phases, while the ANC, being a Fermi-surface probe, provides complementary local information and can identify light-induced gaps even when global topological invariants remain unchanged. Taken together, these results offer useful insights into the topological properties of 2D type-II SDSMs and related systems.
Read the full abstract ▾
Strongly Correlated Electrons
Scalable Quantum Monte Carlo for Shannon-Rényi Entropy: An Experiment-visitable Probe of Quantum Phases and Criticality
Dong-Xu Liu, Zhe Wang, Zenan Liu Yi-Ming Ding et al. (+1 more)
The Shannon-Rényi (SR)
entropy characterizes the probability distribution of many-body wave functions in a chosen basis and is directly accessible from single-shot measurement snapshots in cold-atom experiments, yet its theoretical evaluation in interacting systems carries exponential cost. Here we construct a field-theoretic spacetime
manifold for the SR
entropy in which $q$ replicas are glued at the imaginary-time boundaries, recasting it as a ratio of generalized partition functions amenable to large-scale
quantum Monte Carlo simulation. On this basis we develop a reweight-annealing framework with two complementary strategies: a virtual-parameter scheme interpolating between unglued and fully glued limits via binomial-weighted partial gluing, and a real-parameter scheme using a physical coupling constant as the annealing variable within
stochastic series expansion. Both reduce the computational cost from exponential to
polynomial. Most importantly, we establish for the first time a finite-size scaling theory for the SR
entropy near a
quantum critical point, $S_q=a(g)L^2+S_q^0\left((g-g_c)L^{1/\nu}\right)$; data collapse of its first derivative yields the correlation-length exponent $\nu$ for both the O(3) and Ising universality classes, realized in the
spin-$\frac{1}{2}$ columnar dimerized Heisenberg model and the bilayer Heisenberg-Ising model. The same simulations extract the Goldstone-mode count $N_G=2$ and the $Z_2$ ground-state degeneracy $\ln 2$ from subleading terms. These results elevate the SR
entropy to a standalone, order-parameter-free diagnostic of
quantum criticality with the same scaling status as the
entanglement entropy, and close the loop between theory and
quantum simulation by enabling quantitative benchmarking of experimental snapshots from state-of-the-art
quantum simulators.
Read the full abstract ▾
All authors Dong-Xu Liu, Zhe Wang, Zenan Liu Yi-Ming Ding, Zheng Yan