A5089876659- Quantum many-body systems
- Physics of Superconductivity and Magnetism
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum and electron transport phenomena
- Advanced Condensed Matter Physics
- Opinion Dynamics and Social Influence
- Quantum, superfluid, helium dynamics
- Strong Light-Matter Interactions
- Topological Materials and Phenomena
- Quantum chaos and dynamical systems
- Quantum Chromodynamics and Particle Interactions
- Electronic and Structural Properties of Oxides
- Magnetic and transport properties of perovskites and related materials
- Theoretical and Computational Physics
- Rare-earth and actinide compounds
- Nonlinear Waves and Solitons
- Spectroscopy and Quantum Chemical Studies
- Quantum optics and atomic interactions
- Nonlinear Photonic Systems
- Magnetic properties of thin films
- Semiconductor materials and devices
- Inorganic Fluorides and Related Compounds
- Quantum Mechanics and Non-Hermitian Physics
- Microwave and Dielectric Measurement Techniques
- Algebraic structures and combinatorial models
Delta Institute for Theoretical Physics
2018-2021
University of Amsterdam
2017-2021
Brookhaven National Laboratory
2015-2020
University of Oxford
2012-2016
University of Exeter
2010
We study the effects of integrability-breaking perturbations on nonequilibrium evolution many-particle quantum systems. focus a class spinless fermion models with weak interactions. employ equation motion techniques that can be viewed as generalizations Boltzmann equations. benchmark our method against time-dependent density matrix renormalization group computations and find it to very accurate long interactions are weak. For small integrability breaking, we observe robust prethermalization...
We show that confinement in the quantum Ising model leads to nonthermal eigenstates, both continuum and lattice theories, one (1D) two dimensions (2D). In ordered phase, presence of a confining longitudinal field profound restructuring excitation spectrum, with low-energy two-particle being replaced by discrete "meson" modes (linearly confined pairs domain walls). These exist far into spectrum are atypical, sense expectation values state energy E do not agree microcanonical (thermal)...
We consider quantum quenches in an integrable chain with tuneable-integrability-breaking interactions. In the case where these interactions are weak, we demonstrate that at intermediate times after quench local observables relax to a prethermalized regime, which can be described by density matrix viewed as deformation of generalized Gibbs ensemble. present explicit expressions for approximately conserved charges characterizing this do not find evidence crossover from thermalized regime on...
We present exact analytical solutions for the zero-energy modes of two-dimensional massless Dirac fermions fully confined within a smooth one-dimensional potential $V(x)=\ensuremath{-}\ensuremath{\alpha}/\text{cosh}(\ensuremath{\beta}x)$, which provides good fit profiles existing top-gated graphene structures. show that there is threshold value characteristic strength $\ensuremath{\alpha}/\ensuremath{\beta}$ first mode appears, in striking contrast to nonrelativistic case. A simple...
There is a dichotomy in the nonequilibrium dynamics of quantum many-body systems. In presence integrability, expectation values local operators equilibrate to described by generalized Gibbs ensemble, which retains extensive memory about initial state system. On other hand, generic systems such relax stationary thermal fixed solely energy state. At heart understanding, this eigenstate thermalization hypothesis (ETH): individual eigenstates nonintegrable are thermal, sense that agree with...
We review two important non-perturbative approaches for extracting the physics of low-dimensional strongly correlated quantum systems. Firstly, we start by providing a comprehensive non-Abelian bosonization. This includes an introduction to basic elements conformal field theory as applied systems with current algebra, and orient reader presenting number applications bosonization models large symmetries. then tie this technique into recent advances in ability cold atomic realize complex...
We employ equation of motion techniques to study the non-equilibrium dynamics in a lattice model weakly interacting spinless fermions. Our provides simple setting for analyzing effects weak integrability breaking perturbations on time evolution after quantum quench. establish accuracy method by comparing results at short and intermediate times time-dependent density matrix renormalization group computations. For sufficiently integrability-breaking interactions we always observe...
Over the past two decades, advances in computational algorithms have revealed a curious property of two-dimensional Hubbard model (and related theories) with hole doping: presence close-in-energy competing ground states that display very different physical properties. On one hand, there is complicated state exhibiting intertwined spin, charge, and pair density wave orders. We call this 'type A'. other uniform d-wave superconducting we denote as B'. advocate, support both microscopic...
Although ultrafast manipulation of magnetism holds great promise for new physical phenomena and applications, targeting specific states is held back by our limited understanding how magnetic correlations evolve on timescales. Using resonant inelastic x-ray scattering we demonstrate that femtosecond laser pulses can excite transient magnons at large wavevectors in gapped antiferromagnets, they persist several picoseconds which opposite to what observed nearly gapless magnets. Our work...
We consider the real-time dynamics of an initially localized distinguishable impurity injected into ground state Lieb-Liniger model. Focusing on case where integrability is preserved, we numerically compute time evolution density operator in regimes far from analytically tractable limits. find that undergoes a stuttering motion as it moves and expands. For stationary impurity, interaction-driven formation quasibound with hole background gas leads to arrested expansion---a period...
We report on the tuning of magnetic interactions in superlattices composed single and bilayer SrIrO$_3$ inter-spaced with SrTiO$_3$. Magnetic scattering shows predominately $c$-axis antiferromagnetic orientation moments for justifying these systems as viable artificial analogues bulk Ruddlesden-Popper series iridates. Magnon gaps are observed both superlattices, magnitude gap being reduced to nearly half that its structural analogue, Sr$_3$Ir$_2$O$_7$. assign this modifications anisotropic...
We present experimental and theoretical evidence that an interesting quantum many-body effect---quasiparticle breakdown---occurs in the quasi-one-dimensional spin-$\frac{1}{2}$ Ising-like ferromagnet ${\mathrm{CoNb}}_{2}{\mathrm{O}}_{6}$ its paramagnetic phase at high transverse field as a result of explicit breaking spin inversion symmetry. propose Hamiltonian capturing essential one-dimensional physics determine exchange parameters this model by fitting calculated single-particle...
Computing the non-equilibrium dynamics that follows a quantum quench is difficult, even in exactly solvable models. Results are often predicated on ability to compute overlaps between initial state and eigenstates of Hamiltonian governs time evolution. Except for handful known cases, it generically not possible find these analytically. Here we develop numerical approach preferentially generate states with high starting from ground or an excited Hamiltonian. We use generated states,...
The high-temperature normal state of the unconventional cuprate superconductors has resistivity linear in temperature $T$, which persists to values well beyond Mott-Ioffe-Regel upper bound. At low temperatures, within pseudogap phase, is instead quadratic as would be expected from Fermi liquid theory. Developing an understanding these phases cuprates crucial explain superconductivity. We present a simple explanation for this behavior, terms umklapp scattering electrons. This fits general...
We show that the coupling of homogeneous Heisenberg spin-1/2 ladders in different phases leads to formation interfacial zero energy Majorana bound states. Unlike states at interfaces topological quantum wires, these are void protection and generally susceptible local perturbations host spin system. However, a key message our work is practice they high degree resilience over wide parameter ranges which may make them interesting candidates for applications.
We consider the effects of Umklapp processes in doped two-leg fermionic ladders. These may emerge either at special band fillings or as a result presence external periodic potentials. show that such can lead to profound changes physical properties and particular stabilize pair-density wave phases.
Motivated by recent works aimed at understanding the status of equilibration and eigenstate thermalization hypothesis in theories with confinement, we return to 't Hooft model, large-Nc limit (1 + 1)-d quantum chromodynamics. This has been studied extensively since its inception mid-1970s, various exact results being known, such as quark meson propagators, quark-antiquark interaction vertex, decay amplitude. We then argue this model is an ideal laboratory study non-equilibrium phenomena, it...
We study the excitation spectrum of two-component delta-function interacting bosons confined to a single spatial dimension, Yang-Gaudin Bose gas.We show that there are pronounced finite-size effects in dispersion relations excitations, perhaps best illustrated by spinon particle which exhibits gap at 2k F and finite-momentum roton-like minimum.Such features occur energies far above finite volume gap, vanish slowly as 1/L for fixed number, can persist thermodynamic limit density.Features such...
Motivated by recent works aimed at understanding the status of equilibration and eigenstate thermalization hypothesis in theories with confinement, we return to 't Hooft model, large-$N_c$ limit (1+1)-d quantum chromodynamics. This has been studied extensively since its inception mid-1970s, various exact results being known, such as quark meson propagators, quark-antiquark interaction vertex, decay amplitude. We then argue this model is an ideal laboratory study non-equilibrium phenomena, it...
We consider the non-equilibrium dynamics of two-component one dimensional quantum gases in limit extreme population imbalance where minority species has but a single particle. situation gas is prepared state with spatially localized exciton: particle while density majority vicinity sees depression. Remarkably, we are able to cases contains on order N = 100 particles, comparable that studied experiments cold atomic gases. do so by exploiting integrability together observation excitonic can be...
We consider the Ising chain driven by oscillatory transverse magnetic fields. For certain parameter regimes, we reveal a hidden integrable structure in problem, which allows access to exact time evolution this quantum system. compute time-evolved one- and two-point functions following quench that activates driving. It is shown model does not heat up infinite temperature, despite absence of energy conservation, further discuss generalization family Hamiltonians do appear suffer heating...
In the nested limit of spin-fermion model for cuprates, one-dimensional physics in form half-filled two-leg ladders emerges. We show that renormalization group flow corresponding ladder is towards d-Mott phase, a gapped spin-liquid with short-ranged d-wave pairing correlations, and reveals an intermediate SO(5)$\times$SO(3) symmetry. use results combination memory-function approach to calculate optical conductivity high-frequency regime, where processes within hot spot region dominate...