Title: Designing spin and orbital exchange Hamiltonians with ultrashort electric field transients,
Abstract: We demonstrate how electric fields with arbitrary time profile can be used to
control the time-dependent parameters of spin and orbital exchange
Hamiltonians. Analytic expressions for the exchange constants are derived from
a time-dependent Schrieffer-Wolff transformation, and the validity of the
resulting effective Hamiltonian is verified for the case of a quarter-filled
two-orbital Hubbard model, by comparing to the results of a full nonequilibrium
dynamical mean-field theory simulation. The ability to manipulate Hamiltonians
with arbitrary time-dependent fields, beyond the paradigm of Floquet
engineering, opens the possibility to control intertwined spin and orbital
order using laser or THz pulses which are tailored to minimize electronic
excitations.