Theoretical Physics Colloquium

Quantum Scars in many-body systems

by Prof. Arnab Sen (IACS, Kolkata)

Tuesday, March 2, 2021 from to (Asia/Kolkata)
at Zoom
Description
The eigenstate thermalization hypothesis (ETH) is believed to be true for generic quantum many-body systems and explains how local equilibration is achieved even with purely unitary dynamics. It is equally interesting to understand how ETH might be violated in interacting systems. Two well-known routes are provided by integrability and many-body localization with strong disorder. Here, I discuss a third alternative for non-integrable disorder free systems where ETH is violated due to the presence of some highly athermal eigenstates, called quantum many-body scars, embedded in an otherwise ETH-satisfying spectrum. Their direct physical manifestation is to  cause anomalous dynamics from some simple initial conditions while most initial states rapidly thermalize. As examples, I will discuss two particular spin models in constrained Hilbert spaces, a PXP model and a U(1) quantum link model, both of which can also be mapped to lattice gauge theories and demonstrate two completely different mechanisms for producing quantum many-body scars.