The optimal frequency window for Floquet engineering in optical lattices

TL;DR

This paper investigates the optimal frequency range for Floquet engineering in optical lattices, showing that increasing lattice depth suppresses heating and extends the system's coherence time.

Contribution

It identifies the optimal frequency window for Floquet engineering in optical lattices, demonstrating how lattice depth influences heating suppression and coherence time extension.

Findings

Heating time $ au$ increases faster than tunneling time $ au o au$ with lattice depth.

Optimal frequency window maximizes $ au$, reducing unwanted heating.

Floquet heating suppression improves with deeper optical lattices.

Abstract

The concept of Floquet engineering is to subject a quantum system to time-periodic driving in such a way that it acquires interesting novel properties. It has been employed, for instance, for the realization of artificial magnetic fluxes in optical lattices and, typically, it is based on two approximations. First, the driving frequency is assumed to be low enough to suppress resonant excitations to high-lying states above some energy gap separating a low energy subspace from excited states. Second, the driving frequency is still assumed to be large compared to the energy scales of the low-energy subspace, so that also resonant excitations within this space are negligible. Eventually, however, deviations from both approximations will lead to unwanted heating on a time scale $\tau$. Using the example of a one-dimensional system of repulsively interacting bosons in a shaken optical lattice, we investigate the optimal frequency (window) that maximizes $\tau$. As a main result, we find that, when increasing the lattice depth, $\tau$ increases faster than the experimentally relevant time scale given by the tunneling time $\hbar/J$, so that Floquet heating becomes suppressed.