Loading...
Derniers dépôts, tout type de documents
Chiral Spin Liquids (CSL) based on spin-1/2 fermionic Projected Entangled Pair States (fPEPS) are considered on the square lattice. First, fPEPS approximants of Gutzwiller-projected Chern insulators (GPCI) are investigated by Variational Monte Carlo (VMC) techniques on finite size tori. We show that such fPEPS of finite bond dimension can correctly capture the topological properties of the chiral spin liquid, as the exact GPCI, with the correct topological ground state degeneracy on the torus. Further, more general fPEPS are considered and optimized (on the infinite plane) to describe the CSL phase of a chiral frustrated Heisenberg antiferromagnet. The chiral modes are computed on the edge of a semi-infinite cylinder (of finite circumference) and shown to follow the predictions from Conformal Field Theory. In contrast to their bosonic analogs the (optimized) fPEPS do not suffer from the replication of the chiral edge mode in the odd topological sector.
Non-abelian symmetries are thought to be incompatible with many-body localization, but have been argued to produce in certain disordered systems a broad non-ergodic regime distinct from many-body localization. In this context, we present a numerical study of properties of highly-excited eigenstates of disordered chains with SU(3) symmetry. We find that while weakly disordered systems rapidly thermalize, strongly-disordered systems indeed exhibit non-thermal signatures over a large range of system sizes, similar to the one found in previously studied SU(2) systems. Our analysis is based on the spectral, entanglement, and thermalization properties of eigenstates obtained through large-scale exact diagonalization exploiting the full SU(3) symmetry.
Despite enormous efforts devoted to the study of the many-body localization (MBL) phenomenon, the nature of the high-energy behavior of the Heisenberg spin chain in a strong random magnetic field is lacking consensus. Here, we take a step back by exploring the weak interaction limit starting from the Anderson localized (AL) insulator. Through shift-invert diagonalization, we find that below a certain disorder threshold $h^*$, weak interactions necessarily lead to ergodic instability, whereas at strong disorder the AL insulator directly turns into MBL. This agrees with a simple interpretation of the avalanche theory for restoration of ergodicity. We further map the phase diagram for the generic XXZ model in the disorder $h$-- interaction $\Delta$ plane. Taking advantage of the total magnetization conservation, our results unveil the remarkable behavior of the spin-spin correlation functions: in the regime indicated as MBL by standard observables, their exponential decay undergoes a unique inversion of orientation $\xi_z>\xi_x$. We find that the longitudinal length $\xi_z$ is a key quantity for capturing ergodic instabilities, as it increases with system size near the thermal phase, in sharp contrast to its transverse counterpart $\xi_x$.
In condensed matter, Chiral Spin Liquids (CSL) are quantum spin analogs of electronic Fractional Quantum Hall states (in the continuum) or Fractional Chern Insulators (on the lattice). As the latter, CSL are remarquable states of matter, exhibiting topological order and chiral edge modes. Preparing CSL on quantum simulators like cold atom platforms is still an open challenge. Here we propose a simple setup on a finite cluster of spin-1/2 located at the sites of a square lattice. Using a Resonating Valence Bond (RVB) non-chiral spin liquid as initial state on which fast time-modulations of strong nearest-neighbor Heisenberg couplings are applied, following different protocols (out-of-equilibrium quench or semi-adiabatic ramping of the drive), we show the slow emergence of such a CSL phase. An effective Floquet dynamics, obtained from a high-frequency Magnus expansion of the drive Hamiltonian, provides a very accurate and simple framework fully capturing the out-of-equilibrium dynamics. An analysis of the resulting prepared states in term of Projected Entangled Pair states gives further insights on the topological nature of the chiral phase. Finally, we discuss possible applications to quantum computing.
The physics of skyrmions, and in particular the issue of how to isolate and manipulate them individually, is a subject of major importance nowadays in the community of magnetism. In this article we present an in-depth extension of a study on this issue that was recently proposed by some of the authors [H. D. Rosales, et al. Phys. Rev. Lett. 130, 106703 (2023)]. More precisely, we analyse the competition between skyrmions and a chiral spin liquid in a model on the kagome lattice. We first present an analytical overview of the low-energy states using the Luttinger-Tisza approximation. We then study the effect of thermal fluctuations thanks to large-scale Monte-Carlo simulations, and explore the entire parameter space with a magnetic field B, in-plane D xy and outof-plane D z Dzyaloshinskii-Moriya interactions. While skyrmions and the chiral spin liquid live in different regions of the parameter space, we show how to bring them together, stabilizing a skyrmion fluid in between; a region where the density of well-defined skyrmions can be tuned before obtaining an ordered phase. We investigate in particular the melting of the skyrmion solid. Our analysis also brings to light a long-range ordered phase with Z3 symmetry. At last, we initiate the study of this rich magnetic background on conduction electrons that are coupled to the local spins. We study how the different chiral magnetic textures stabilized in this model (skyrmion solid, liquid and gas and chiral spin liquid) induce a topological Quantum Hall effect. We observe in the ordered skyrmion phase the appearance of Landau levels which persist even in the skyrmion-liquid regime and gradually disappear as the skyrmion density decreases to form a gas.
Sujets
Strong interaction
Valence bond crystals
Supraconductivité
Théorie de la matière condensée
Quantum physics
Condensed matter theory
Aimants quantiques
Chaines de spin
Superconductivity cond-matsupr-con
Quasiparticle
Bosons de coeur dur
Condensed Matter
Monte-Carlo quantique
Heisenberg model
Electronic structure and strongly correlated systems
Basse dimension
Atomic Physics physicsatom-ph
Atom
Quantum dimer models t-J model superconductivity magnetism
Condensed matter physics
Strongly Correlated Electrons cond-matstr-el
Réseaux de tenseurs
Dimension
Antiferromagnetism
Ground state
Physique quantique
Champ magnétique
Systèmes fortement corrélés
0270Ss
Benchmark
7510Kt
Entanglement quantum
Correlation
Liquid
Quantum dimer models t-J model
Strongly Correlated Electrons
7510Jm
Numerical methods
Condensed Matter Electronic Properties
7127+a
Strongly correlated systems
Physique de la matière condensée
Classical spin liquid
Méthodes numériques
Anyons
Plateaux d'aimantation
Dimeres
Kagome lattice
Frustration
Dirac spin liquid
Polaron
Low-dimensional systems
Bose glass
7540Cx
7130+h
Gas
Antiferromagnetic conductors
Chaines de spin1/2
Arrays of Josephson junctions
6470Tg
Advanced numerical methods
Tensor networks
Chaînes des jonctions
Quantum Gases cond-matquant-gas
Critical phenomena
Many-body problem
Apprentissage automatique
Boson
Color
Quantum information
Magnétisme quantique
Network
T-J model
Anti-ferromagnetism
Spin chain
Antiferromagnétisme
Disorder
Deconfinement
Solids
FOS Physical sciences
Low dimension
Spin
High-Tc
7540Mg
Entanglement
Spin liquids
Machine learning
Magnetism
Superconductivity
Collective modes
Collinear
Thermodynamical
Variational quantum Monte Carlo
Magnetic quantum oscillations
Variational Monte Carlo
Électrons fortement corrélés
Excited state
Quantum magnetism
Condensed matter