Spin-momentum coupled Bose-Einstein condensates with lattice band pseudospins

TL;DR

This paper demonstrates a new form of spin-momentum coupling in Bose-Einstein condensates by coupling s- and p-bands in a driven optical lattice, enabling exploration of topological quantum phases.

Contribution

It introduces a novel method to realize spin-momentum coupling using lattice band pseudospins in a driven optical lattice, expanding quantum simulation capabilities.

Findings

Observation of s-p band hybrid Floquet-Bloch bands.

Measurement of quasimomentum matching theoretical models.

Potential for engineering new quantum matter.

Abstract

The quantum emulation of spin-momentum coupling (SMC), a crucial ingredient for the emergence of topological phases, is currently drawing considerable interest. In previous quantum gas experiments, typically two atomic hyperfine states were chosen as pseudospins. Here, we report the observation of a new kind of SMC achieved by loading a Bose-Einstein condensate (BEC) into periodically driven optical lattices. The s- and p-bands of a static lattice, which act as pseudospins, are coupled through an additional moving lattice which induces a momentum dependent coupling between the two pseudospins, resulting in s-p hybrid Floquet-Bloch bands. We investigate the band structures by measuring the quasimomentum of the BEC for different velocities and strengths of the moving lattice and compare our measurements to theoretical predictions. The realization of SMC with lattice bands as pseudospins paves the way for engineering novel quantum matter using hybrid orbital bands.