Pair condensation in a dilute Bose gas with Rashba spin–orbit coupling

Abstract

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 inplane 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.

BCS-pairing state of a dilute Bose gas with spin-orbit coupling

“…In the fermion case, the only s-wave interaction is the interspecies interaction, whereas in the boson case there are both inter-species and intra-species interactions. In the case with two-bosons with Rashba SOC [45], due to statistics only the intra-species bound state is affected by SOC, while in the fermion case the inter-species bound state is affected.…”

“…The realization of SOC in cold atoms may offer the opportunity to realize the long-sought BCS pairing state of Bose atoms. A pairing condensation in a dilute Bose gas with 2D Rashba SOC and weak intra-species attraction can be stablized by inter-species repulsion [45], but the intra-species attraction can also lead to phase separation which may become an experimental obstacle. In this work, we investigate the pairing state of Bose gas * yinlan@pku.edu.cn with an isotropic 3D SOC.…”

Bardeen-Cooper-Schrieffer–type pairing in a spin- 12 Bose gas with spin-orbit coupling

“…This null result is quite surprising given its non-trivial fermionic counterpart, where a bound state with b = 0 is known to exist for any a s no matter how weak g is as long as g = 0 [25]. However, we note that the intra-component pairing of bosons with Rashba SOC is similar to the fermion problem [20].…”

“…Motivated by the recent creations of two-component quantum gases with two-dimensional SOCs [16][17][18][19], here we revisit this old-standing problem in a so-called spin-1 2 Bose gas. Having a dilute Bose gas with shortranged density-density interactions in mind, we consider an inter-component attraction U ↑↓ = U ↓↑ = −g < 0, and analyze how the presence of a SOC affects the resultant pairing correlations [20,21]. The mechanical collapse is counteracted by the Hartree terms arising from the intra-component repulsions [7,[21][22][23].…”

Energetics and structural properties of two- and three-boson systems in the presence of one-dimensional spin-orbit coupling

“…Because of this, the two-boson system is investigated in detail. In contrast to the extensively-studied two-fermion systems with various types of spin-orbit coupling [42][43][44][45][46][47][48][49][50][51], comparatively works on the two-boson systems with 2D and 3D spin-orbit coupling are found in the literature [50,[52][53][54][55][56].…”