Physics at Virginia

"Coherence Properties of Spin-Orbit Coupled Condensates"

Supriyo Ghosh , UVA
[Host: Dima Pesin]

Realization of artificial spin-orbit (SO) coupling in the cold atom systems has opened a broad spectrum of phenomena to be observed experimentally in bosonic systems. The physics of spontaneous symmetry breaking leads to the several exotic quantum phases such as superfluid and more recently the supersolid. In the latter case, both diagonal and off-diagonal long-range order, although being mutually exclusive, are present and it breaks two U(1) symmetries. One of the ways to realize this supersolid phase is using the condensates of Alkali atoms in a double well optical lattice. Such SO coupled systems have interesting phase diagrams depending on the interaction and SO coupling strength. In presence of weak coupling and negligible inter-species interaction the system remains in the phase known as striped phase or miscible phase. In this case, the Raman beam couples two condensates and provides a momentum kick along a perpendicular direction, which indeed leads to a one-dimensional density modulation due to interference.  Two continuous symmetries are broken by the superfluid phase and the breaking of translation symmetry along one direction, satisfying the definition of a supersolid. Spinor BECs and their relative phase coherence has been a topic of interest for quite some time. The dephasing of the relative phase has important implications in the density modulation and its experimental observation.  I will consider a specific realization of a pseudo-spin-1/2 BEC, in which the two spin components are represented by spatially separated low-lying states in a double-well potential. I will demonstrate that even if the system is initialized with a given relative phase between the two components, there is an apparent dephasing of the relative phase. The dephasing is a consequence of a very weak interaction between the spin species. Furthermore, I will demonstrate that the dephasing rate is a non-monotonic function of the Raman coupling strength. The minimum of the dephasing rate corresponds to the critical value of the Raman coupling, above which miscible to immiscible phase transition occurs.

Condensed Matter Seminar
Tuesday, April 25, 2023
12:00 PM
Rotunda, Room 102
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