Speaker
Jonas Kjäll
Description
Many-body localization is closely connected to some
fundamental questions of quantum mechanics, like how and why
quantum systems thermalize. It can protect quantum order at
elevated temperatures and can potentially be important in
the development of quantum memories. Many-body localization
occurs in isolated quantum systems when Anderson
localization persists in the presence of finite
interactions. Despite strong evidence for the existence of a
many-body localization transition a reliable extraction of
the critical disorder strength has been difficult due to a
large drift with system size in the studied quantities. In
this talk I describe the challenges involved in this problem
and explain our approaches, based on entanglement entropy,
to understand it: (i) the variance of the half-chain
entanglement entropy of exact eigenstates and (ii) the long
time change in entanglement after a local quench from an
exact eigenstate. With this we can estimate the critical
disorder strength and its energy dependence. We investigate
these quantities in a disordered quantum Ising chain that
also has disorder protected quantum order at large disorder
strength and provide evidence for it being a separate
transition.
