Universal trimers emerging from a spin-orbit coupled Fermi sea

TL;DR

This paper demonstrates the emergence of a universal three-body bound state, a trimer, in a spin-orbit coupled Fermi gas, stabilized by spectral symmetry and many-body effects, with potential detection via spectroscopy.

Contribution

It reveals a universal trimer state induced by spin-orbit coupling, stabilized by many-body effects, and maps the phase diagram including trimers, dimers, and polarons.

Findings

Universal trimer exists in 2D spin-orbit coupled Fermi gas.

Trimer stability is enhanced by particle-hole fluctuations.

Phase diagram includes trimers, dimers, and polarons.

Abstract

We report the existence of a universal trimer state induced by an impurity interacting with a two-component spin-orbit coupled Fermi gas in two dimensions. In the zero-density limit with a vanishing Fermi sea, the trimer is stabilized by the symmetry of the single-particle spectrum under spin-orbit coupling, and is therefore {\it universal} against the short-range details of the interaction potential. When the Fermi energy increases, we show that the trimer is further stabilized by particle-hole fluctuations over a considerable parameter region. We map out the phase diagram consisting of trimers, dimers, and polarons, and discuss the detection of these states using radio-frequency spectroscopy. The universal trimer revealed in our work is a direct manifestation of intriguing three-body correlations emerging from a many-body environment, which, in our case, is cooperatively supported by the single-particle spectral symmetry and the collective particle-hole excitations.