Floquet spin and spin-orbital Hamiltonians and doublon-holon generations in periodically driven Mott insulators

Abstract

We consider Mott insulators driven by periodic coherent laser radiation, using both single orbital and multi-orbital models, noting that the latter is of more interest in solid state systems. We derive general expressions for the resulting periodically driven spin models and spin-orbital models using time-dependent perturbation theory. First, we show that the effective exchange interactions of the Floquet Hamiltonians are highly tunable by the frequency, amplitude, and polarization of the laser. Second, we take the effect of finite bandwidth of excitations into account and study possible heating effects. Using the same formalism with a slight modification we also consider the small frequency regime and study the dielectric breakdown of Mott insulators.

Colloquium: Nonthermal pathways to ultrafast control in quantum materials

“…Strong spin-orbit coupled multi-orbital compounds constitute a natural generalization of such a nonequilibrium separation of charge and spin degrees of freedom (Arakawa and Yonemitsu, 2021;Hejazi et al, 2019;Liu et al, 2018;Sriram and Claassen, 2021), which could allow for Floquet engineering while mitigating heating. In the orthorhombic titanates, the partially-filled t 2g manifold has been proposed as a prime target for optical manipulation of effective Kugel-Khomskii spin-orbital interactions.…”

Comparing the influence of Floquet dynamics in various Kitaev-Heisenberg materials

“…In this paper we study the capabilities of Floquet engineering, for α-RuCl 3 as well as for α-Li 2 IrO 3 and Na 2 IrO 3 . First we consider an approximate approach to capture heating around the resonances [32] in order to identify frequencies where it is small. This gives an insight on which of these materials are well suited for Floquet engineering.…”

“…The paper is structured as follows: In Sec. II we derive the effective Floquet Hamiltonian for the Kitaev-Heisenberg model, applying the results of [7,32,33] to the already well established Kitaev-Heisenberg model [34,35]. We introduce the off-resonance limit of the model as well as a possibility to describe the system near resonances.…”

Excitonic effects in twisted bilayer graphene

“…Particularly, inducing the twist between the layers in the bilayer graphene leads to the formation of the moiré-like superlattice structures [1][2][3][4][5][6][7][8][9]. It has been shown both experimentally [10][11][12][13] and theoretically [14][15][16][17][18][19][20][21] that when this angle is close to the so-called magic angles, the electronic band structure becomes flat near the zero Fermi energy, which is a direct consequence of the strong interlayer correlations in the twisted bilayer graphene (tBLG). The flat bands lead to the Mott-like insulating states with the intervalley coherence, at the half-filling, arising at the magic twist angles [16,17].…”

“…It has been shown both experimentally [10][11][12][13] and theoretically [14][15][16][17][18][19][20][21] that when this angle is close to the so-called magic angles, the electronic band structure becomes flat near the zero Fermi energy, which is a direct consequence of the strong interlayer correlations in the twisted bilayer graphene (tBLG). The flat bands lead to the Mott-like insulating states with the intervalley coherence, at the half-filling, arising at the magic twist angles [16,17]. The excitonic effects in the layered two-dimensional structures [22] represent another important interest due to their possible direct applications in various fields of the modern material nanosciences, including photovoltaics and photocatalytic [23], technological use as nanometre-scale light sources [24], exciton-valleytronics [25] and photodetectors.…”