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    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...

    Université de Fribourg

    Nonequilibrium dynamical mean-field theory and its applications

    Aoki, Hideo ; Tsuji, Naoto ; Eckstein, Martin ; Kollar, Marcus ; Oka, Takashi ; Werner, Philipp

    In: Reviews of Modern Physics, 2014, vol. 86, no. 2, p. 779–837

    The study of nonequilibrium phenomena in correlated lattice systems has developed into one of the most active and exciting branches of condensed matter physics. This research field provides rich new insights that could not be obtained from the study of equilibrium situations, and the theoretical understanding of the physics often requires the development of new concepts and methods. On the...

    Université de Fribourg

    Ordered phases in the Holstein-Hubbard model: Interplay of strong Coulomb interaction and electron-phonon coupling

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

    In: Physical Review B, 2013, vol. 88, no. 12, p. 125126

    We study the Holstein-Hubbard model at half filling to explore ordered phases including superconductivity (SC), antiferromagnetism (AF), and charge order (CO) in situations where the electron-electron and electron-phonon interactions are strong (comparable to the electronic bandwidth). The model is solved in the dynamical mean-field approximation with a continuous-time quantum Monte Carlo...