Designing spin and orbital exchange Hamiltonians with ultrashort electric field transients

TL;DR

This paper presents a method to control spin and orbital exchange interactions in quantum materials using arbitrary time-dependent electric fields, enabling precise manipulation of quantum states beyond traditional Floquet techniques.

Contribution

It derives analytic expressions for exchange constants under time-dependent fields and validates them with nonequilibrium dynamical mean-field theory simulations.

Findings

Analytic exchange constants derived from time-dependent Schrieffer-Wolff transformation.

Validation of effective Hamiltonian with nonequilibrium dynamical mean-field theory.

Potential for controlling spin and orbital order with tailored laser or THz pulses.

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.