Ultrafast and reversible control of the exchange interaction in Mott insulators

TL;DR

This paper demonstrates that electric field modulation can ultrafastly and reversibly control the exchange interaction in Mott insulators, enabling manipulation of spin dynamics and potential applications in condensed matter and cold atom systems.

Contribution

It introduces a method to control the exchange interaction in Mott insulators using time-periodic electric fields, including sign reversal at strong driving.

Findings

$J_{ex}$ can be enhanced or reduced depending on frequency.

Sign reversal of $J_{ex}$ achieved with strong driving.

Reversal of quantum spin dynamics demonstrated.

Abstract

The strongest interaction between microscopic spins in magnetic materials is the exchange interaction $J_\text{ex}$. Therefore, ultrafast control of $J_\text{ex}$ holds the promise to control spins on ultimately fast timescales. We demonstrate that time-periodic modulation of the electronic structure by electric fields can be used to reversibly control $J_\text{ex}$ on ultrafast timescales in extended antiferromagnetic Mott insulators. In the regime of weak driving strength, we find that $J_\text{ex}$ can be enhanced and reduced for frequencies below and above the Mott gap, respectively. Moreover, for strong driving strength, even the sign of $J_\text{ex}$ can be reversed and we show that this causes time reversal of the associated quantum spin dynamics. These results suggest wide applications, not only to control magnetism in condensed matter systems, for example, via the excitation of spin resonances, but also to assess fundamental questions concerning the reversibility of the quantum many-body dynamics in cold atom systems.