Rashbon bound states associated with a spherical spin-orbit coupling in an ultracold Fermi gas with an $s$-wave interaction

Abstract

We investigate the formation of rashbon bound states and strong-coupling effects in an ultracold Fermi gas with a spherical spin-orbit interaction, $H_{\mathrm{so}}=\lambda \mathbf{p}\cdot \sigma$ (where $\sigma =({\sigma }_x,{\sigma }_y,{\sigma }_z)$ are Pauli matrices). Extending the strong-coupling theory developed by Nozières and Schmitt-Rink (NSR) to include this spin-orbit coupling, we determine the superfluid phase transition temperature $T_{\mathrm{c}}$, as functions of the strength of a pairing interaction $U_s$, as well as the spin-orbit coupling strength $\lambda$. Evaluating poles of the NSR particle-particle scattering matrix describing fluctuations in the Cooper channel, we clarify the region where rashbon bound states dominate the superfluid phase transition in the $U_s$-$\lambda$ phase diagram. Since the antisymmetric spin-orbit interaction $H_{\mathrm{so}}$ breaks the inversion symmetry of the system, rashbon bound states naturally have, not only a spin-singlet and even-parity symmetry, but also a spin-triplet and odd-parity symmetry. Thus, our results would be also useful for the study of this parity mixing effect in the BCS-BEC crossover regime of a spin-orbit coupled Fermi gas.

7 pages, 3 figues, proceedings of the international symposium on Quantum Fluids and Solids QFS2015

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Cited by in corpus (2)

• Superfluid transition temperature and fluctuation theory of spin-orbit and Rabi-coupled fermions with tunable interactions
• Interaction-Range Effects and Universality in the BCS-BEC Crossover of Spin-Orbit Coupled Fermi Gases