We study the impact of quenched disorder on the dynamics of locally constrained quantum spin chains, that describe 1D arrays of Rydberg atoms in both the frozen (Ising-type) and dressed (XY-type) regime. Performing large-scale numerical experiments, we observe no trace of many-body localization even at large disorder. Analyzing the role of quenched disorder terms in constrained systems we show that they act in two, distinct and competing ways: as an on-site disorder term for the basic excitations of the system, and as an interaction between excitations. The two contributions are of the same order, and as they compete (one towards localization, the other against it), one does never enter a truly strong disorder, weak interaction limit, where many-body localization occurs. Such a mechanism is further clarified in the case of XY-type constrained models: there, a term which would represent a bona fide local quenched disorder term acting on the excitations of the clean model must be written as a series of nonlocal terms in the unconstrained variables. Our observations provide a simple picture to interpret the role of quenched disorder that could be immediately extended to other constrained models or quenched gauge theories.We study the impact of quenched disorder on the dynamics of locally constrained quantum spin chains, that describe 1D arrays of Rydberg atoms in both the frozen (Ising-type) and dressed (XY-type) regime. Performing large-scale numerical experiments, we observe no trace of many-body localization even at large disorder. Analyzing the role of quenched disorder terms in constrained systems we show that they act in two, distinct and competing ways: as an on-site disorder term for the basic excitations of the system, and as an interaction between excitations. The two contributions are of the same order, and as they compete (one towards localization, the other against it), one does never enter a truly strong disorder, weak interaction limit, where many-body localization occurs. Such a mechanism is further clarified in the case of XY-type constrained models: there, a term which would represent a bona fide local quenched disorder term acting on the excitations of the clean model must be written as a series of nonlocal terms in the unconstrained variables. Our observations provide a simple picture to interpret the role of quenched disorder that could be immediately extended to other constrained models or quenched gauge theories.

arXiv:2103.14020Physical Review LettersSep 14, 202135 citations

Critical behavior induced by quenched disorder

A. Nihat Berker

Physica A Statistical Mechanics and its ApplicationsMar 1, 1993129 citations

Thermalization of a disordered interacting system under an interaction quench

Eric Dohner, Hanna Terletska, Herbert F. Fotso

Although most studies of strongly correlated systems away from equilibrium have focused on clean systems, it is well known that disorder may significantly modify observed properties in various nontrivial ways. The nonequilibrium interplay of interaction and disorder in these systems thus requires further investigation. In the present paper, we use the recently developed nonequilibrium $\text{DMFT}+\text{CPA}$ embedding scheme, that combines both the dynamical mean field theory (DMFT) and the coherent potential approximation (CPA) nonequilibrium extensions, to characterize the relaxation and the thermalization of a disordered interacting system described by the Anderson-Hubbard model under an interaction quench. The system, initially in equilibrium at a given temperature, has the interaction abruptly switched from zero to a finite value at a given time. To investigate the role of disorder, we use our effective medium approach to calculate, for different values of the final interaction and of the disorder strength, the distribution functions as the system evolves in time. This allows us to determine the effective temperature after the quench and to analyze the effects of disorder on the thermalization for various interaction strengths. We find that, for moderate interactions after the interaction quench, disorder can tune the final temperature of the system across a broad range of values with increased disorder strength leading to lower effective temperature.Although most studies of strongly correlated systems away from equilibrium have focused on clean systems, it is well known that disorder may significantly modify observed properties in various nontrivial ways. The nonequilibrium interplay of interaction and disorder in these systems thus requires further investigation. In the present paper, we use the recently developed nonequilibrium $\text{DMFT}+\text{CPA}$ embedding scheme, that combines both the dynamical mean field theory (DMFT) and the coherent potential approximation (CPA) nonequilibrium extensions, to characterize the relaxation and the thermalization of a disordered interacting system described by the Anderson-Hubbard model under an interaction quench. The system, initially in equilibrium at a given temperature, has the interaction abruptly switched from zero to a finite value at a given time. To investigate the role of disorder, we use our effective medium approach to calculate, for different values of the final interaction and of the disorder strength, the distribution functions as the system evolves in time. This allows us to determine the effective temperature after the quench and to analyze the effects of disorder on the thermalization for various interaction strengths. We find that, for moderate interactions after the interaction quench, disorder can tune the final temperature of the system across a broad range of values with increased disorder strength leading to lower effective temperature.

arXiv:2303.06495Physical review. B./Physical review. BOct 3, 20235 citations

Disorder effects

Springer eBooksSep 27, 20070 citations

Destabilization of the U(1) Dirac spin liquid phase on the triangular lattice by quenched disorder

Santanu Dey

It has been recently demonstrated [Song et al., Nature Comm. 10, 4254 (2019), Iqbal et al., Phys. Rev. B 93, 144411 (2016)] that the staggered $\pi$ -flux Dirac spin liquid phase on the non-bipartite triangular lattice may be stable in the clean limit. However, quenched disorder plays a crucial role in determining whether such a phase can be experimentally viable. The effective low-energy description of Dirac spin liquids in $(2+1)$ dimensions is given by the compact quantum electrodynamics ( $\rm cQED_{2+1}$ ) which admits monopoles. It is already known that generic quenched random perturbations to the non-compact version of $\rm QED_{2+1}$ (where monopoles are absent) lead to strong-coupling instabilities. In this work we study $\rm cQED_{2+1}$ in the presence of a class of time-reversal invariant quenched disorder perturbations. We show that in this model, random non-abelian vector potentials make the symmetry-allowed monopole operators more relevant. The disorder induced under-screening of monopoles thus generically makes the gapless spin liquid phase fragile.It has been recently demonstrated [Song et al., Nature Comm. 10, 4254 (2019), Iqbal et al., Phys. Rev. B 93, 144411 (2016)] that the staggered $\pi$-flux Dirac spin liquid phase on the non-bipartite triangular lattice may be stable in the clean limit. However, quenched disorder plays a crucial role in determining whether such a phase can be experimentally viable. The effective low-energy description of Dirac spin liquids in $(2+1)$ dimensions is given by the compact quantum electrodynamics ($\rm cQED_{2+1}$) which admits monopoles. It is already known that generic quenched random perturbations to the non-compact version of $\rm QED_{2+1}$ (where monopoles are absent) lead to strong-coupling instabilities. In this work we study $\rm cQED_{2+1}$ in the presence of a class of time-reversal invariant quenched disorder perturbations. We show that in this model, random non-abelian vector potentials make the symmetry-allowed monopole operators more relevant. The disorder induced under-screening of monopoles thus generically makes the gapless spin liquid phase fragile.

Aug 27, 20201 citation

\text{DMFT}+\text{CPA}

embedding scheme, that combines both the dynamical mean field theory (DMFT) and the coherent potential approximation (CPA) nonequilibrium extensions, to characterize the relaxation and the thermalization of a disordered interacting system described by the Anderson-Hubbard model under an interaction quench. The system, initially in equilibrium at a given temperature, has the interaction abruptly switched from zero to a finite value at a given time. To investigate the role of disorder, we use our effective medium approach to calculate, for different values of the final interaction and of the disorder strength, the distribution functions as the system evolves in time. This allows us to determine the effective temperature after the quench and to analyze the effects of disorder on the thermalization for various interaction strengths. We find that, for moderate interactions after the interaction quench, disorder can tune the final temperature of the system across a broad range of values with increased disorder strength leading to lower effective temperature.

It has been recently demonstrated [Song et al., Nature Comm. 10, 4254 (2019), Iqbal et al., Phys. Rev. B 93, 144411 (2016)] that the staggered

\pi

-flux Dirac spin liquid phase on the non-bipartite triangular lattice may be stable in the clean limit. However, quenched disorder plays a crucial role in determining whether such a phase can be experimentally viable. The effective low-energy description of Dirac spin liquids in

(2+1)

dimensions is given by the compact quantum electrodynamics (

\rm cQED_{2+1}

) which admits monopoles. It is already known that generic quenched random perturbations to the non-compact version of

\rm QED_{2+1}

(where monopoles are absent) lead to strong-coupling instabilities. In this work we study

\rm cQED_{2+1}

in the presence of a class of time-reversal invariant quenched disorder perturbations. We show that in this model, random non-abelian vector potentials make the symmetry-allowed monopole operators more relevant. The disorder induced under-screening of monopoles thus generically makes the gapless spin liquid phase fragile.