Physics (Internal)

Artificial Gauge Fields in Driven Optical Lattices

This event is part of the Condensed Matter Theory Seminar Series.

Abstract: Quantum gases provide a controllable and isolated environment for the investigation of model Hamiltonians, reaching from the weakly-interacting to the strongly-correlated regime. However, as the constituent particles of these gases are typically neutral they do not respond to electromagnetic fields via the Lorentz force. This is a central limitation towards the simulation of various solid state models involving electromagnetic fields. In recent years the creation of synthetic gauge fields for ultracold neutral atoms has developed to a promising field that allows overcoming this limitation. In particular, it has been demonstrated that periodically driven optical lattices can stroboscopically mimic the effects of gauge fields. In this talk, we report on the experimental realization of a spin model with coupled continuous and discrete degrees of freedom on a periodically driven triangular lattice. As a result of an artificial staggered magnetic field, the bosonic atoms in the lattice show persistent circular currents in analogy to the cyclotron motion of electrons in magnetic fields. The direction of this mass flow provides a discrete Ising variable, while the local phase of the coherent state on each lattice site represents a continuous variable. By measuring the magnetization of the systems we observe a thermally driven Ising-type phase transition from an ordered, (anti-)ferromagnetic to an unordered, paramagnetic state. Further, we discuss our recent proposal to engineer a time-periodic and spin-dependent drive in order to realize spin-dependent tunnel matrix elements and spin-orbit coupling in an optical lattice.