Ultrafast modification of Hubbard $U$ in a strongly correlated material: ab initio high-harmonic generation in NiO

TL;DR

This paper demonstrates that a strong nonresonant laser can dynamically modify the Hubbard U parameter in NiO on femtosecond timescales, affecting high-harmonic generation and opening new avenues for controlling strongly correlated materials.

Contribution

It introduces a method to modulate the Hubbard U in real-time using laser excitation, enhancing understanding of ultrafast control in correlated electron systems.

Findings

Hubbard U can be modified on femtosecond timescales by laser excitation.

Dynamically modulated U influences high-harmonic generation in NiO.

Potential for laser-induced phase transitions in strongly correlated materials.

Abstract

Engineering effective electronic parameters is a major focus in condensed matter physics. Their dynamical modulation opens the possibility of creating and controlling physical properties in systems driven out of equilibrium. In this work, we demonstrate that the Hubbard $U$, the on-site Coulomb repulsion in strongly correlated materials, can be modified on femtosecond time scales by a strong nonresonant laser excitation in the prototypical charge transfer insulator NiO. Using our recently developed time-dependent density functional theory plus self-consistent $U$ (TDDFT+U) method, we demonstrate the importance of a dynamically modulated $U$ in the description of the high-harmonic generation of NiO. Our study opens the door to novel ways of modifying effective interactions in strongly correlated materials via laser driving, which may lead to new control paradigms for field-induced phase transitions and perhaps laser-induced Mott insulation in charge-transfer materials.