Ultrafast Modification of HubbardUin a Strongly Correlated Material:Ab initioHigh-Harmonic Generation in NiO

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 Letter, we demonstrate that the Hubbard U, the widely used on-site Coulomb repulsion in strongly correlated materials, can be modified on femtosecond timescales by a strong nonresonant laser pulse excitation in the prototypical charge-transfer insulator NiO. Using our recently developed time-dependent density-functional theory plus self-consistent 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.

Dynamics of photodoped charge transfer insulators

“…The electric field pulse transfers charge from the p bands to the upper Hubbard band, which results in relative band shifts. Similar band shifts have been observed in a recent time-dependent density functional theory (TDDFT)+U study of NiO [12], while the present study shows that charge fluctuations strongly enhance this effect. The strong plasmon coupling in the photodoped state leads to a substantial broadening of the d and p bands, which implies that dynamical correlation effects (beyond HF) are essential for the description of the ligand bands, in contrast to equilibrium.…”

“…Experiments have demonstrated, e.g., the switching to a hidden metallic state in 1T-TaS 2 [4], or light-induced enhancements of superconductivity [5,6] and excitonic order [7]. Related are theoretical proposals to modify the band structure [8,9] or interactions by electronic excitations [10][11][12] or phonon driving [13][14][15][16][17][18][19].…”

Cavity quantum electrodynamical Chern insulator: Towards light-induced quantized anomalous Hall effect in graphene

“…Similarly it will be interesting to investigate how effective couplings in materials, such as dynamical Hubbard U [60][61][62][63], the exchange interaction [39,64,65], or electronphonon couplings [66][67][68][69], can be affected by quantum rather than classical light.…”

Floquet DMFT Analysis of High Harmonic Generation in Mott Insulators

“…We also discussed the similarities and differences between the HHG in Mott insulators and semiconductors. Recent experiments have motivated numerous theoretical efforts to understand the HHG in correlated systems such as disordered systems [23,24], strongly correlated systems [25][26][27] as well as spin systems [28]. We hope that our present work and these studies will stimulate further explorations of new HHG sources in consented matters.…”