Theoretical Physics Colloquium

Memories in Quantum Many-Body Dynamics: The case of Many Body Localization

by Prof. Rajdeep Sensarma (TIFR)

Tuesday, September 24, 2019 from to (Asia/Kolkata)
at AG69
A basic tenet of equilibrium statistical mechanics is that long-time averages of local quantities in a many body system do not depend on initial state of the system. They can be calculated from a distribution which depends only on the Hamiltonian of the system. Strongly disordered interacting systems violate this; i.e. they retain memories of initial states at long times and do not thermalize: a phenomenon known as many body localization. To understand this behaviour, which is seen experimentally, we construct a non equilibrium field theory which can describe quantum dynamics starting from arbitrary initial conditions (Textbook versions require initial system to be in thermal equilibrium). Our new formalism provides exact universal answers for long time memory retention in disordered non-interacting systems. We will also show that weakly interacting systems retain finite memory of initial states. However, the long time effective description of the interacting system is widely different from that of the non-interacting one.