Synthetic Magnetic Fields for Ultracold Neutral Atoms
Yu-Ju Lin, Robert L. Compton, Karina K. Jimenez Garcia, James V. Porto, Ian B. Spielman
Neutral atomic Bose condensates and degenerate Fermi gases have realized important many-body phenomena in their most simple and essential forms, without many of the complexities usually associated with material systems. A rich source of physics in electronic systems arises from the Lorentz force for charged particles in a magnetic field; among the most intriguing examples are the fractional quantum Hall states in 2D electron systems in strong magnetic fields. For neutral atomic gases, pioneering demonstrations of synthetic magnetic fields relied on the equivalence of the Lorentz force and the Coriolis force in rotating systems, where the appearance of quantized vortices is a hallmark of superfluidity in a magnetic field. However, due to technical issues limiting the maximum rotation velocity and the metastable nature of the rotating state, new approaches are required to reach the quantum-Hall regime. Some approaches to circumvent these limitations involve spatially-dependent optical coupling between internal states of the atoms, yielding a Berry's phase sufficient to create large synthetic magnetic fields. Here we experimentally realize such synthetic fields for the first time, observing up to 12 vortices in a Bose-Einstein condensate (BEC) of neutral -87Rb atoms.