Dielectric breakdown of Mott insulators – doublon production and doublon heating

We study the relaxation of the Holstein model after a sudden switch-on of the interaction by means of the nonequilibrium dynamical mean field theory, with the self-consistent Migdal approximation as an impurity solver. We show that there exists a qualitative change in the thermalization dynamics as the interaction is varied in the weak-coupling regime. On the weaker interaction side of this crossover, the phonon oscillations are damped more rapidly than the electron thermalization timescale, as determined from the relaxation of the electron momentum distribution function. On the stronger interaction side, the relaxation of the electrons becomes faster than the phonon damping. In this regime, despite long-lived phonon oscillations, a thermalized momentum distribution is realized temporarily. The origin of the "thermalization crossover" found here is traced back to different behaviors of the electron and phonon self-energies as a function of the electron-phonon coupling. In addition, the importance of the phonon dynamics is demonstrated by comparing the self-consistent Migdal results with those obtained with a simpler Hatree-Fock impurity solver that neglects the phonon self-energy. The latter scheme does not properly describe the evolution and thermalization of isolated electron-phonon systems.

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“…57, 58 The results in Section III C will confirm that the phonon effectively act as heat bath within the HF approximation.…”

Section: (B)mentioning

confidence: 66%

Interaction quench in the Holstein model: Thermalization crossover from electron- to phonon-dominated relaxation

et al. 2015

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“…This result is consistent with the previous literature. 24,25,46 In addition, we revealed WS peaks originating from manybody processes, which are absent in semiconductors. These states can be connected to peaks and humps in the induced DC current through the tunneling formula.…”

Section: Discussionmentioning

confidence: 79%

Nonequilibrium steady states of electric field driven Mott insulators

Murakami

Werner

2018

Phys. Rev. B

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We present a systematic study of the nonequilibrium steady states (NESS) in Mott insulators driven by DC or AC electric fields, based on the Floquet dynamical mean-field theory. The results are analyzed using a generalized tunneling formula for the current, which is reminiscent of the Meir-Wingreen formula and provides insights into the relevant physical processes. In the DC case, the spectrum of the NESSs exhibits Wannier-Stark (WS) states associated with the lower and upper Hubbard bands. In addition, there emerge WS sidebands from many-body states. Using the tunneling formula, we demonstrate that the tunneling between these WS states leads to peaks or humps in the induced DC current. In the AC case, we cover a wide parameter range of excitation frequencies and field strengths to clarify the crossover from field-induced tunneling behavior in the DC limit to nonequilibrium states dominated by multiphoton absorption in the AC limit. In the crossover regime, the single-particle spectrum is characterized by a coexistence of Floquet sidebands and WS peaks, and the current and double occupation exhibits a nontrivial dependence on the field strength. The tunneling formula works quantitatively well even in the AC case, and we use it to discuss the potential cooperation of tunneling and multi-photon processes in the crossover regime. The tunneling formula and its simplified versions also provide physical insights into the high-harmonic generation in Mott insulators.

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“…The nonequilibrium expansion dynamics of a fermionic particle cloud following a confinement quench and its slowing down due to doublon formation has been studied experimentally in a 2D optical lattice [4] and theoretically by 2D quantum simulations using nonequilibrium Green functions (NEGF) [8]. Also, the external control of doublons by an interaction quench [9], by external electric fields [10][11][12][13][14][15] or by optical excitation [16] has been proposed. Furthermore, the dynamics of heteronuclear doublons [17] and the spatial transfer of doublons via topological edge states [18] have been studied.…”

mentioning

confidence: 99%