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    Université de Fribourg

    Nonequilibrium steady states of electric field driven Mott insulators

    Murakami, Yuta ; Werner, Philipp

    In: Physical Review B, 2018, vol. 98, no. 7, p. 075102

    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...

    Université de Fribourg

    High-harmonic generation in Mott insulators

    Murakami, Yuta ; Eckstein, Martin ; Werner, Philipp

    In: Physical Review Letters, 2018, vol. 121, no. 5, p. 057405

    Using Floquet dynamical mean-field theory, we study the high-harmonic generation in the time-periodic steady states of wide-gap Mott insulators under ac driving. In the strong-field regime, the harmonic intensity exhibits multiple plateaus, whose cutoff energies εcut=U+mE0 scale with the Coulomb interaction U and the maximum field strength E0. In this regime, the created doublons and holons...

    Université de Fribourg

    Nonthermal switching of charge order: Dynamical slowing down and optimal control

    Schüler, Michael ; Murakami, Yuta ; Werner, Philipp

    In: Physical Review B, 2018, vol. 97, no. 15, p. 155136

    We investigate the laser-induced dynamics of electronically driven charge-density- wave (CDW) order. A comprehensive mean-field analysis of the attractive Hubbard model in the weak-coupling regime reveals ultrafast switching and ultrafast melting of the order via a nonthermal pathway. The resulting nonequilibrium phase diagram exhibits multiple distinct regimes of the order parameter dynamics...

    Université de Fribourg

    Enhanced pairing susceptibility in a photodoped two-orbital Hubbard model

    Werner, Philipp ; Strand, Hugo U. R. ; Hoshino, Shintaro ; Murakami, Yuta ; Eckstein, Martin

    In: Physical Review B, 2018, vol. 97, no. 16, p. 165119

    Local spin fluctuations provide the glue for orbital-singlet spin-triplet pairing in the doped Mott insulating regime of multiorbital Hubbard models. At large Hubbard repulsion U, the pairing susceptibility is nevertheless tiny because the pairing interaction cannot overcome the suppression of charge fluctuations. Using nonequilibrium dynamical mean field simulations of the two-orbital...

    Université de Fribourg

    Floquet prethermalization in the resonantly driven Hubbard model

    Herrmann, Andreas ; Murakami, Yuta ; Eckstein, Martin ; Werner, Philipp

    In: EPL (Europhysics Letters), 2017, vol. 120, no. 5, p. 57001

    We demonstrate the existence of long-lived prethermalized states in the Mott insulating Hubbard model driven by periodic electric fields. These states, which also exist in the resonantly driven case with a large density of photo-induced doublons and holons, are characterized by a nonzero current and an effective temperature of the doublons and holons which depends sensitively on the driving...

    Université de Fribourg

    Photoinduced enhancement of excitonic order

    Murakami, Yuta ; Golež, Denis ; Eckstein, Martin ; Werner, Philipp

    In: Physical Review Letters, 2017, vol. 119, no. 24, p. 247601

    We study the dynamics of excitonic insulators coupled to phonons using the time- dependent mean-field theory. Without phonon couplings, the linear response is given by the damped amplitude oscillations of the order parameter with a frequency equal to the minimum band gap. A phonon coupling to the interband transfer integral induces two types of long-lived collective oscillations of the...

    Université de Fribourg

    Nonequilibrium steady states and transient dynamics of conventional superconductors under phonon driving

    Murakami, Yuta ; Tsuji, Naoto ; Eckstein, Martin ; Werner, Philipp

    In: Physical Review B, 2017, vol. 96, no. 4, p. 045125

    We perform a systematic analysis of the influence of phonon driving on the superconducting Holstein model coupled to heat baths by studying both the transient dynamics and the nonequilibrium steady state (NESS) in the weak and strong electron-phonon coupling regimes. Our study is based on the nonequilibrium dynamical mean-field theory, and for the NESS we present a Floquet formulation ...

    Université de Fribourg

    Damping of the collective amplitude mode in superconductors with strong electron-phonon coupling

    Murakami, Yuta ; Werner, Philipp ; Tsuji, Naoto ; Aoki, Hideo

    In: Physical Review B, 2016, vol. 94, no. 11, p. 115126

    We study the effect of strong electron-phonon interactions on the damping of the Higgs amplitude mode in superconductors by means of nonequilibrium dynamical mean-field simulations of the Holstein model. In contrast to the BCS dynamics, we find that the damping of the Higgs mode strongly depends on the temperature, becoming faster as the system approaches the transition temperature. The...

    Université de Fribourg

    Multiple amplitude modes in strongly coupled phonon-mediated superconductors

    Murakami, Yuta ; Werner, Philipp ; Tsuji, Naoto ; Aoki, Hideo

    In: Physical Review B, 2016, vol. 93, no. 9, p. 94509

    We study collective amplitude modes of the superconducting order parameter in strongly coupled electron-phonon systems described by the Holstein model using the nonequilibrium dynamical mean-field theory with the self-consistent Migdal approximation as an impurity solver. The frequency of the Higgs amplitude mode is found to coincide with the superconducting gap even in the strongly coupled...

    Université de Fribourg

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

    Murakami, Yuta ; Werner, Philipp ; Tsuji, Naoto ; Aoki, Hideo

    In: Physical Review B, 2015, vol. 91, no. 4, p. 045128

    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...