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Résumé |
When an approximate conservation law protects a degree of freedom, even weak
perturbations can cause a strong response in that quantity and can drive the
system far from its equilibrium steady state. Examples of quantum platforms with
many conserved quantities are integrable and many-body localized (MBL) systems,
and in realistic setups their conservation laws are only approximate.
I will present the theory of weakly driven and open systems with
approximate conservation laws. I will show that generalized Gibbs ensembles can
approximate the slow dynamics and steady-state of nearly integrable systems when
perturbations are not only static but also weakly drive the system and couple it
to baths. Besides fundamental importance, this also has practical implications:
by pumping spin-chain materials approximately described by the Heisenberg model,
one can stabilize steady states with immense heat and spin currents, since these
are approximately conserved even in a real material. Pumping in approximate
conservation laws can also be utilized to detect key features of MBL systems
even when coupled to a thermalizing bath. The strength of coupling to driving
and bath (e.g., phonons) has a role similar to the finite temperature in the T=0
quantum phase transitions. I will discuss how driving disordered systems gives a
new route to study MBL, numerically, and experimentally.
Lange, Lenarcic, Rosch, Pumping approximately integrable systems, Nat. Commun.
8, 15767 (2017).
Lange, Lenarcic, Rosch, Time-dependent generalized Gibbs ensembles in open
quantum systems, Phys. Rev. B 97, 165138 (2018).
Lenarcic, Altman, Rosch, Activating many-body localization in solids by driving
with light, Phys. Rev. Lett. 121, 267603 (2018). |
