January 24 2019

28 till 30.01.2019: Visit of Alessio Lerose (SISSA, Trieste)

Alessio Lerose (SISSA, Trieste) will visit us from Monday 28.01.2019 to Wednesday 30.01.2019 .

He will give a talk in our group seminar on Tuesday 29.01.2019 at 10:30 in room 4.18.

Non-equilibrium phenomena in driven long-range interacting spin systems

I will discuss peculiar phenomena that arise in the coherent quantum dynamics of long-range interacting systems driven out of equilibrium. In the first part, I will focus on spin systems with a competition of long- and short-range interactions, and show that the dynamics following a quench near a dynamical instability can exhibit collective chaotic behavior, in that the asymptotic magnetic ordering can be extremely sensitive to the quench parameters and initial conditions. This phenomenon is universal, as it is determined by the effect of fluctuating spin-wave modes on the motion of collective degrees of freedom in a multiple-well landscape. [Phys. Rev. Lett. 120, 130603 (2018), arxiv:1807.09797] In the second part, I will discuss the dynamical stabilization of magnetically-ordered phases of matter under the effect of global periodic drives, which would be unstable in static conditions. I will show how these phases represent a clear many-body quantum analog of the so-called Kapitza pendulum. Indeed, a fundamental question is whether, by modulating a single global parameter in a many-body system, one can stabilize an otherwise unstable phase of matter against all possible fluctuations of its microscopic degrees of freedom. I will demonstrate that such stabilization is actually possible and that these quantum many-body Kapitza phases can be detected in current state-of-the-art experiments with trapped ions. [arxiv:1803.04490] In the third part, I will illustrate the analytical mechanism responsible for the slow (logarithmic) growth of entanglement entropy in out-of-equilibrium long-range interacting spin systems, which has been reported in several recent numerical studies, and illustrate its quantitative link with collective spin-squeezing, which has long been recognized as a witness of many-particle entanglement. [arxiv:1811.05505]



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