Multiphoton interband excitations of quantum gases in driven optical lattices

12 May 2015

Photo: AG Sengstock

Periodically driven quantum systems, so called Floquet systems, are described by a time-independent effective Hamiltonian. This allows for realizing artificial gauge fields, magnetic fields and spin-orbit coupling, for neutral particles. Understanding excitations that may arise from the external driving is a crucial prerequisite for the utilization of this so called “Floquet engineering”.

Here we report on the observation of multiphoton absorption processes for quantum gases in shaken optical lattices. Periodic inertial forcing, induced by a spatial motion of the lattice potential, drives multiphoton interband excitations of up to the 9th order. The occurrence of such excitation features is systematically investigated with respect to the potential depth and the driving amplitude. Ab initio calculations of resonance positions as well as numerical evaluation of their strengths exhibit a good agreement with experimental data. Our findings set the stage for reaching novel phases of quantum matter by tailoring appropriate driving schemes.

Phys. Rev. A 92 043621 (2015)