title: Spin-momentum coupled Bose-Einstein condensates with lattice band pseudospins.
abstract: The quantum emulation of spin-momentum coupling, 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 spin-momentum coupling achieved by loading a Bose-Einstein condensate 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 that 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 Bose-Einstein condensate for different velocities and strengths of the moving lattice, and compare our measurements to theoretical predictions. The realization of spin-momentum coupling with lattice bands as pseudospins paves the way for engineering novel quantum matter using hybrid orbital bands.
authors.affiliation: Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Khamehchi
authors.affiliation: Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA.
authors.forename: Chunlei
authors.initials: C
authors.lastname: Qu
authors.affiliation: Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: Mossman
authors.affiliation: Department of Physics, The University of Texas at Dallas, Richardson, Texas 75080, USA.
authors.forename: Chuanwei
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA.
authors.forename: P
authors.initials: P
authors.lastname: Engels