29 research outputs found
Permutation Symmetric Critical Phases in Disordered Non-Abelian Anyonic Chains
Topological phases supporting non-abelian anyonic excitations have been
proposed as candidates for topological quantum computation. In this paper, we
study disordered non-abelian anyonic chains based on the quantum groups
, a hierarchy that includes the FQH state and the proposed
Fibonacci state, among others. We find that for odd these
anyonic chains realize infinite randomness critical {\it phases} in the same
universality class as the permutation symmetric multi-critical points of
Damle and Huse (Phys. Rev. Lett. 89, 277203 (2002)). Indeed, we show that the
pertinent subspace of these anyonic chains actually sits inside the symmetric sector of the Damle-Huse model, and this symmetry stabilizes the phase.Comment: 13 page
Non-equilibrium critical scaling and universality in a quantum simulator
Universality and scaling laws are hallmarks of equilibrium phase transitions
and critical phenomena. However, extending these concepts to non-equilibrium
systems is an outstanding challenge. Despite recent progress in the study of
dynamical phases, the universality classes and scaling laws for non-equilibrium
phenomena are far less understood than those in equilibrium. In this work,
using a trapped-ion quantum simulator with single-ion resolution, we
investigate the non-equilibrium nature of critical fluctuations following a
quantum quench to the critical point. We probe the scaling of spin fluctuations
after a series of quenches to the critical Hamiltonian of a long-range Ising
model. With systems of up to 50 spins, we show that the amplitude and timescale
of the post-quench fluctuations scale with system size with distinct universal
critical exponents. While a generic quench can lead to thermal critical
behaviour, we find that a second quench from one critical state to another
(i.e. a double quench) results in critical behaviour that does not have an
equilibrium counterpart. Our results demonstrate the ability of quantum
simulators to explore universal scaling beyond the equilibrium paradigm.Comment: 10 pages, 5 figures. Supplementary information contains 18 pages, 10
figure
Experimental realization of a topological Anderson insulator
We experimentally demonstrate that disorder can induce a topologically non-trivial phase. We implement this “Topological Anderson Insulator” in arrays of evanescently coupled waveguides and demonstrate its unique features
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Absence of thermalization in finite isolated interacting Floquet systems
Conventional wisdom suggests that the long-time behavior of isolated interacting periodically driven (Floquet) systems is a featureless maximal-entropy state characterized by an infinite temperature. Efforts to thwart this uninteresting fixed point include adding sufficient disorder to realize a Floquet many-body localized phase or working in a narrow region of drive frequencies to achieve glassy nonthermal behavior at long time. Here we show that in clean systems the Floquet eigenstates can exhibit nonthermal behavior due to finite system size. We consider a one-dimensional system of spinless fermions with nearest-neighbor interactions where the interaction term is driven. Interestingly, even with no static component of the interaction, the quasienergy spectrum contains gaps and a significant fraction of the Floquet eigenstates, at all quasienergies, have nonthermal average doublon densities. We show that this nonthermal behavior arises due to emergent integrability at large interaction strength and discuss how the integrability breaks down with power-law dependence on system size
Reaction diffusion equation in the ultra cold coexisting atomic and molecular condensates and the importance of Feshbach interaction
We consider a gas of bosonic atoms near a Feshbach resonance. The dynamics of the atomic
and molecular condensates can be described in the limit of small fluctuations by a set of
coupled nonlinear Gross Piteaviskii equations. In the case of a strong atom-molecule conversion,
the system has an integral motion for the spatially uniform solutions which exhibits temporal
oscillation. The possible consequence of this oscillation may be the existence of Josephson like
current in the condensates which has been investigated