Spin orbit coupling in a dilute gas Bose-Einstein condensate

Dekun Luo, Lan Yin

We study the Bardeen–Cooper–Shrieffer (BCS) pairing state of a two-component Bose gas with a symmetric spin–orbit coupling (SOC). In the dilute limit at low temperature, this system is essentially a dilute gas of diatomic molecules. We compute the effective mass of the molecule and find that it is anisotropic in momentum space. The critical temperature of the pairing state is about eight times smaller than the Bose–Einstein condensation (BEC) transition temperature of an ideal Bose gas with the same density.

Brandon Anderson, Tudor D. Stanescu, Victor M. Galitski

Y.-J. Lin, Karina Jiménez-García, Ian B. Spielman

Dekun Luo, Lan Yin

We study a two-component Bose gas with a symmetric spin-orbit coupling, and find that two atoms can form a bound state with any intra- or inter-species scattering length. Consequently, in the dilute limit, the BCS-pairing state of bosons can be formed with weakly attractive interspecies and repulsive intraspecies interactions. The quasiparticle excitation energies are anisotropic due to spin-orbit coupling. This BCS-pairing state is energetically favored over Bose-Einstein condensation (BEC) of atoms at low densities. As the density increases, there is a first-order transition from the BCS to BEC states.

Robert Niffenegger, Abraham J. Olson, Chuan-Hsun Li +1 more

Rong Li, Lan Yin

We show that in a two-component Bose gas with Rashba spin–orbit coupling (SOC), two atoms can form bound states (Rashbons) with any intra-species scattering length. At zero center-of-mass momentum, there are two degenerate Rashbons due to time-reversal symmetry, but the degeneracy is lifted at finite in-plane momentum with two different effective masses. A stable Rashbon condensation can be created in a dilute Bose gas with attractive intra-species and repulsive inter-species interactions. The critical temperature of Rashbon condensation is about six times smaller than the Bose–Einstein condensation transition temperature of an ideal Bose gas. Due to the Rashba SOC, excitations in the Rashbon condensation phase are anisotropic in momentum space.