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.