Dynamically Assisted Tunneling in the Floquet Picture

We study how tunneling through a potential barrier $V(x)$ can be enhanced by an additional harmonically oscillating electric field ${\mathfrak E}(t)={\mathfrak E}_0\cos(\omega t)$. To this end, we transform into the Kramers-Henneberger frame and calculate the coupled Floquet channels numerically. We find distinct signatures of resonances when the incident energy $E$ equals the driving frequency $\omega=E$ which clearly shows the breakdown of the time-averaged potential approximation. As a simple model for experimental applications (e.g., in solid state physics), we study the rectangular potential, which can also be benchmarked with respect to analytical results. Finally, we consider the truncated Coulomb potential relevant for nuclear fusion.