Special Colloquium
Department of Physics, NCU
Atomtronics with a spin: Ramsey response and nonequilibrium dynamics in cold quantum gases
Speaker
Dr. Jhih-Shih You (游至仕博士)
Institute for Theoretical Solid State Physics, IFW Dresden, Germany
Date 2020.03.09(Mon)
Time 12:00PM
Place S4-625
Abstract
Non-equilibrium dynamics is at the heart of many problems in science and technology, from the physics of heavy ion collisions to the operation of electronic devices. In solid state systems, the direct observation of the evolution of electrons and spins on the Fermi timescale is still notoriously challenging. In atomic quantum gases, however, the fermions are much heavier and the densities are far lower, bringing shortest response time into the experimentally accessible scale.
In this talk, I will introduce an ultracold atom setup, analogous to a spintronics device, which generates spin transport induced by an impurity atom immersed in a spin-imbalanced two-component Fermi gas. By manipulating the internal spin degrees of freedom of the Fermi system, one can directly count the number of spins in each reservoir to investigate the full counting statistics of spin flips. Moreover, using Ramsey interferometry, the dynamical impurity response can be measured. Since the impurity interacts with a many-body environment that is out of equilibrium, this setup provides a way to realize the non-equilibrium orthogonality catastrophe. For the impurity response at late time, we are able to derive analytical expressions, which reveal an intimate connection of the decay rate of the Ramsey contrast and the full counting statistics of spin flips.