Experimental Realization of Strong Effective Magnetic Fields in an Optical Lattice

TLDR

In an optical lattice, atomic hopping acquires a phase equivalent to the Aharonov–Bohm phase of a charged particle in a staggered magnetic field of about one flux quantum per plaquette. The study aims to generate large tunable effective magnetic fields for ultracold atoms using Raman‑assisted tunneling in an optical superlattice. Raman‑assisted tunneling in the superlattice is employed, and the local phase acquired is measured, revealing time‑reversal symmetry breaking of the underlying Hamiltonian. The magnetic frustration induces a degenerate ground state, and single‑atom quantum cyclotron orbits are directly observed.

Abstract

We use Raman-assisted tunneling in an optical superlattice to generate large tunable effective magnetic fields for ultracold atoms. When hopping in the lattice, the accumulated phase shift by an atom is equivalent to the Aharonov-Bohm phase of a charged particle exposed to a staggered magnetic field of large magnitude, on the order of 1 flux quantum per plaquette. We study the ground state of this system and observe that the frustration induced by the magnetic field can lead to a degenerate ground state for noninteracting particles. We provide a measurement of the local phase acquired from Raman-induced tunneling, demonstrating time-reversal symmetry breaking of the underlying Hamiltonian. Furthermore, the quantum cyclotron orbit of single atoms in the lattice exposed to the magnetic field is directly revealed.