Spin-orbital-angular-momentum-coupled quantum gases

TL;DR

This paper reviews recent theoretical and experimental advances in spin-orbital-angular-momentum (SOAM) coupling in quantum gases, highlighting new quantum phases, topological properties, and experimental realizations in cold atom systems.

Contribution

It provides a comprehensive overview of engineering SOAM coupling in neutral atoms, discusses unique single-particle physics, and introduces novel quantum phases and topological phenomena in Bose and Fermi gases.

Findings

Observation of phase transitions in SOAM-coupled Bose gases

Proposal of stable giant vortex in SOAM-coupled Fermi superfluid

Discussion of topological properties in SOAM-coupled Fermi superfluids

Abstract

We briefly review the recent progress of theories and experiments on spin-orbital-angular-momentum (SOAM)-coupled quantum gases. The coupling between the intrinsic degree of freedom of particles and their external orbital motions widely exists in universe, and leads to a broad variety of fundamental phenomena both in the classical physics and quantum mechanics. Recent realization of synthetic SOAM coupling in cold atoms has attracted a great deal of attention, and stimulates a large amount of considerations on exotic quantum phases in both Bose and Fermi gases. In this review, we present a basic idea of engineering SOAM coupling in neutral atoms, starting from a semiclassical description of atom-light interaction. Unique features of the single-particle physics in the presence of SOAM coupling are discussed. The intriguing ground-state quantum phases of weakly interacting Bose gases are introduced, with emphasis on a so-called angular stripe phase, which has yet been observed at present. It is demonstrated how to generate a stable giant vortex in a SOAM-coupled Fermi superfluid. We also discuss topological characters of a Fermi superfluid in the presence of SOAM coupling. We then introduce the experimental achievement of SOAM coupling in $^{87}$Rb Bose gases and its first observation of phase transitions. The most recent development of SOAM-coupled Bose gases in experiments is also summarized. Regarding the controllability of ultracold quantum gases, it opens a new era, on the quantum simulation point of view, to study the fundamental physics resulted from SOAM coupling as well as newly emergent quantum phases.