Repulsion-to-attraction transition in correlated electron systems triggered by a monocycle pulse

TL;DR

This paper demonstrates that a carefully shaped monocycle electric pulse can induce a permanent transition from repulsive to attractive electron interactions in the Hubbard model, driven by nonadiabatic population shifts.

Contribution

It reveals a novel mechanism for interaction switching in correlated electron systems using nonadiabatic pulse shaping and nonequilibrium dynamical mean-field theory.

Findings

Interaction can be switched from repulsive to attractive without energy dissipation.

A nonadiabatic momentum shift $oldsymbol{ ext{delta}}$ causes the transition.

Negative-temperature states are achieved through specific pulse conditions.

Abstract

We study the time evolution of the Hubbard model driven by a half-cycle or monocycle pulsed electric field F(t) using the nonequilibrium dynamical mean-field theory. We find that for properly chosen pulse shapes the electron-electron interaction can be effectively and permanently switched from repulsive to attractive if there is no energy dissipation. The physics behind the interaction conversion is a nonadiabatic shift $\delta$ of the population in momentum space. When $\delta\sim\pi$, the shifted population relaxes to a negative-temperature state, which leads to the interaction switching. Due to electron correlation effects $\delta$ deviates from the dynamical phase $\phi=\int dt F(t)$, which enables the seemingly counterintuitive repulsion-to-attraction transition by a monocycle pulse with $\phi=0$.