Phase diagram, band structure and density of states in two-dimensional attractive Fermi-Hubbard model with Rashba spin-orbit coupling

TL;DR

This paper investigates the phase diagram, band structure, and density of states in a 2D attractive Fermi-Hubbard model with Rashba SOC, revealing conditions for topological superfluidity and its experimental implications.

Contribution

It provides a detailed analysis of the phase transition to topological superfluidity, highlighting the effects of SOC strength, Zeeman field, and doping in a 2D Fermi-Hubbard model.

Findings

Topological superfluid transition occurs under specific Zeeman and SOC conditions.

The topological superfluid region exhibits a dome-shaped dependence on SOC strength.

DOS features four peaks associated with topology changes in quasiparticle spectra.

Abstract

Based on the two-dimensional (2D) attractive Fermi-Hubbard model with Rashba spin-orbit coupling (SOC), the SOC strength and Zeeman field dependences of the phase diagram are investigated by calculating the pairing gap self-consistently. The results reveal that the phase transition from the BCS superfluid to the topological superfluid happens under proper Zeeman field strength and SOC strength. In particular, in contrast to the BCS superfluid decreasing monotonically as the SOC strength increasing, the topological superfluid region shows a dome with the SOC strength increasing. An optimal region in the phase diagram to find the topological superfluid can be found, which is important to realize the topological superfluid in optical lattice experimentally. Then we obtain the change of both band structure and density of states (DOS) during the topological phase transition, and explain the four peaks of DOS in the topological superfluid by the topology change of the low-energy branch of quasiparticle energy spectra. Moreover, the topological superfluid can be suppressed by the doping concentration.