Title: Dynamical control of electron-phonon interactions with high-frequency light,
Abstract: This work addresses the one-dimensional problem of Bloch electrons when they
are rapidly driven by a homogeneous time-periodic light and linearly coupled to
vibrational modes. Starting from a generic time-periodic electron-phonon
Hamiltonian, we derive a time-independent effective Hamiltonian that describes
the stroboscopic dynamics up to the third order in the high-frequency limit.
This yields nonequilibrium corrections to the electron-phonon coupling that are
controllable dynamically via the driving strength. This shows in particular
that local Holstein interactions in equilibrium are corrected by nonlocal
Peierls interactions out of equilibrium, as well as by phonon-assisted hopping
processes that make the dynamical Wannier-Stark localization of Bloch electrons
impossible. Subsequently, we revisit the Holstein polaron problem out of
equilibrium in terms of effective Green functions, and specify explicitly how
the binding energy and effective mass of the polaron can be controlled
dynamically. These tunable properties are reported within the weak- and
strong-coupling regimes since both can be visited within the same material when
varying the driving strength. This work provides some insight into controllable
microscopic mechanisms that may be involved during the multicycle laser
irradiations of organic molecular crystals in ultrafast pump-probe experiments,
although it should also be suitable for realizations in shaken optical lattices
of ultracold atoms.