JQI Seminar 11/18/13

Speaker: Andrew Daley

Institution: University of Pittsburgh

Abstract:

One of the key challenges in current experiments with cold atoms in optical lattices is the realization of lower temperatures required for the preparation of many interesting quantum phases. In this context, it is very important to be able to characterise and control the competing heating processes. These include, for example, spontaneous emissions from incoherent scattering of the lattice light. Such heating processes give rise to decoherence of many-body states, and the resulting dynamics can be highly sensitive to the form of the state. Moreover, there is often a separation of timescales between some excitations that thermalize rapidly, and others that do not properly thermalize in the duration of an experimental run. This can strongly modify, and even reduce the overall effects of the heating processes.

I will discuss some of our recent work in this direction, where we explore the relaxation of a system of bosons in an optical lattice in 1D after decoherence due to spontaneous emission events. For simple observables, we find regimes in which the system relaxes rapidly to values in agreement with a thermal distribution, and others where thermalization does not occur on typical experimental timescales. Because spontaneous emissions lead effectively to a local quantum quench, this behaviour is strongly dependent on the low-energy spectrum of the Hamiltonian, and undergoes a qualitative change at the Mott Insulator-superfluid transition point. These results have important implications for the understanding of thermalization after localized quenches in isolated quantum gases, as well as the characterization of heating in experiments. I will also briefly discuss the heating of two-species fermions in spin-ordered states due to spontaneous emission events.


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