5,172 research outputs found
Flux quench in a system of interacting spinless fermions in one dimension
We study a quantum quench in a one-dimensional spinless fermion model
(equivalent to the XXZ spin chain), where a magnetic flux is suddenly switched
off. This quench is equivalent to imposing a pulse of electric field and
therefore generates an initial particle current. This current is not a
conserved quantity in presence of a lattice and interactions and we investigate
numerically its time-evolution after the quench, using the infinite
time-evolving block decimation method. For repulsive interactions or large
initial flux, we find oscillations that are governed by excitations deep inside
the Fermi sea. At long times we observe that the current remains non-vanishing
in the gapless cases, whereas it decays to zero in the gapped cases. Although
the linear response theory (valid for a weak flux) predicts the same long-time
limit of the current for repulsive and attractive interactions (relation with
the zero-temperature Drude weight), larger nonlinearities are observed in the
case of repulsive interactions compared with that of the attractive case.Comment: 10 pages, 10 figures; v2: Added references. Figures are refined and
animations are added. Corrected typos. Published versio
Chaos and relative entropy
One characterization of a chaotic system is the quick delocalization of
quantum information (fast scrambling). One therefore expects that in such a
system a state quickly becomes locally indistinguishable from its
perturbations. In this paper we study the time dependence of the relative
entropy between the reduced density matrices of the thermofield double state
and its perturbations in two dimensional conformal field theories. We show that
in a CFT with a gravity dual, this relative entropy exponentially decays until
the scrambling time. This decay is not uniform. We argue that the early time
exponent is universal while the late time exponent is sensitive to the
butterfly effect. This large answer breaks down at the scrambling time,
therefore we also study the relative entropy in a class of spin chain models
numerically. We find a similar universal exponential decay at early times,
while at later times we observe that the relative entropy has large revivals in
integrable models, whereas there are no revivals in non-integrable models.Comment: 34+11 pages, 8 figure
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