Rapidly Rotating Atomic Gases

TL;DR

This paper reviews the theoretical developments in the physics of rapidly rotating atomic Bose gases, focusing on vortex formation, dense vortex regimes, and connections to fractional quantum Hall states, with implications for experiments and future research.

Contribution

It provides a comprehensive overview of the equilibrium properties and phases of rapidly rotating Bose gases, including novel regimes and strongly correlated states, bridging mean-field and quantum Hall physics.

Findings

Vortex arrays form in rotating Bose gases similar to superfluid helium.

Dense vortex regimes allow reduction to lowest Landau level descriptions.

Predicted strongly correlated phases analogous to fractional quantum Hall states.

Abstract

This article reviews developments in the theory of rapidly rotating degenerate atomic gases. The main focus is on the equilibrium properties of a single component atomic Bose gas, which (at least at rest) forms a Bose-Einstein condensate. Rotation leads to the formation of quantized vortices which order into a vortex array, in close analogy with the behaviour of superfluid helium. Under conditions of rapid rotation, when the vortex density becomes large, atomic Bose gases offer the possibility to explore the physics of quantized vortices in novel parameter regimes. First, there is an interesting regime in which the vortices become sufficiently dense that their cores -- as set by the healing length -- start to overlap. In this regime, the theoretical description simplifies, allowing a reduction to single particle states in the lowest Landau level. Second, one can envisage entering a regime of very high vortex density, when the number of vortices becomes comparable to the number of particles in the gas. In this regime, theory predicts the appearance of a series of strongly correlated phases, which can be viewed as {\it bosonic} versions of fractional quantum Hall states. This article describes the equilibrium properties of rapidly rotating atomic Bose gases in both the mean-field and the strongly correlated regimes, and related theoretical developments for Bose gases in lattices, for multi-component Bose gases, and for atomic Fermi gases. The current experimental situation and outlook for the future are discussed in the light of these theoretical developments.