Crystallization of bosonic quantum Hall states in a rotating quantum gas
Abstract
The dominance of interactions over kinetic energy lies at the heart of strongly correlated quantum matter, from fractional quantum Hall liquids^{1}, to atoms in optical lattices^{2} and twisted bilayer graphene^{3}. Crystalline phases often compete with correlated quantum liquids, and transitions between them occur when the energy cost of forming a density wave approaches zero. A prime example occurs for electrons in highstrength magnetic fields, where the instability of quantum Hall liquids towards a Wigner crystal^{49} is heralded by a rotonlike softening of density modulations at the magnetic length^{7,1012}. Remarkably, interacting bosons in a gauge field are also expected to form analogous liquid and crystalline states^{1321}. However, combining interactions with strong synthetic magnetic fields has been a challenge for experiments on bosonic quantum gases^{18,21}. Here we study the purely interactiondriven dynamics of a Landau gauge BoseEinstein condensate^{22} in and near the lowest Landau level. We observe a spontaneous crystallization driven by condensation of magnetorotons^{7,10}, excitations visible as density modulations at the magnetic length. Increasing the cloud density smoothly connects this behaviour to a quantum version of the KelvinHelmholtz hydrodynamic instability, driven by the sheared internal flow profile of the rapidly rotating condensate. At long times the condensate selforganizes into a persistent array of droplets separated by vortex streets, which are stabilized by a balance of interactions and effective magnetic forces.
 Publication:

Nature
 Pub Date:
 January 2022
 DOI:
 10.1038/s41586021041702
 arXiv:
 arXiv:2106.11300
 Bibcode:
 2022Natur.601...58M
 Keywords:

 Condensed Matter  Quantum Gases;
 Condensed Matter  Strongly Correlated Electrons;
 Nonlinear Sciences  Pattern Formation and Solitons;
 Physics  Fluid Dynamics;
 Quantum Physics
 EPrint:
 Nature 601, 5862 (2022)