Synthetic magnetic fields for ultracold neutral atoms

Abstract

Neutral atomic Bose condensates and degenerate Fermi gases have been used to realize important many-body phenomena in their most simple and essential forms, without many of the complexities usually associated with material systems. However, the charge neutrality of these systems presents an apparent limitation-a wide range of intriguing phenomena arise from the Lorentz force for charged particles in a magnetic field, such as the fractional quantum Hall effect in two-dimensional electron systems. The limitation can be circumvented by exploiting the equivalence of the Lorentz force and the Coriolis force to create synthetic magnetic fields in rotating neutral systems. This was demonstrated by the appearance of quantized vortices in pioneering experiments on rotating quantum gases, a hallmark of superfluids or superconductors in a magnetic field. However, because of technical issues limiting the maximum rotation velocity, the metastable nature of the rotating state and the difficulty of applying stable rotating optical lattices, rotational approaches are not able to reach the large fields required for quantum Hall physics. Here we experimentally realize an optically synthesized magnetic field for ultracold neutral atoms, which is evident from the appearance of vortices in our Bose-Einstein condensate. Our approach uses a spatially dependent optical coupling between internal states of the atoms, yielding a Berry's phase sufficient to create large synthetic magnetic fields, and is not subject to the limitations of rotating systems. With a suitable lattice configuration, it should be possible to reach the quantum Hall regime, potentially enabling studies of topological quantum computation.

Thermodynamic properties of rotating trapped ideal Bose gases

“…In this case, atoms behave like charged particles in magnetic field. The "synthetic" magnetic field has already been realized in experiments and can be produced significantly large, which makes it hopefully to achieve the fast-rotating limit [14][15][16].…”

“…More recently, the so-called "synthetic" magnetic field approach is developed [14][15][16], which creates an effective gauge potential A for neutral atoms by means of optical field [17][18][19], instead of rotating the frame. In this case, atoms behave like charged particles in magnetic field.…”

Ultracold quantum gases and lattice systems: quantum simulation of lattice gauge theories

“…A most exciting development are synthetic background gauge fields, in order to access, for example, the fractional quantum Hall effect or topological insulators with atoms. Such synthetic gauge fields can mimic an external magnetic field [41][42][43][44][45][46][47][48][49][50].…”

Some exact Bradlow vortex solutions

“…Although applications for the Bradlow equation may not seem immediate, we would like to consider this as an approximation to a physical system. Bose-Einstein condensates with constant magnetic fields exist experimentally [13] and vortices -global vortices (i.e. ungauged vortices) -are created in such a way that the magnetic field is constant even around the vortices, and so perhaps the Bradlow equation can be used as a rough description in this case.…”