Jong E. Han

Electric-field-driven resistive switching in dissipative Hubbard model

We study how strongly correlated electrons on a dissipative lattice evolve out of equilibrium under a constant electric field, focusing on the extent of the linear regime and hysteretic nonlinear effects at higher fields. We access the nonequilibrium steady states, nonperturbatively in both the field and the electronic interactions, by means of a nonequilibrium dynamical mean-field theory in the Coulomb gauge. The linear response regime, limited by Joule heating, breaks down at fields much smaller than the quasiparticle energy scale. For large electronic interactions, strong but experimentally accessible electric fields can induce a resistive switching by driving the strongly correlated metal into a Mott insulator. We predict a nonmonotonic upper switching field due to an interplay of particle renormalization and the field-driven temperature. Hysteretic I-V curves suggest that the nonequilibrium current is carried through a spatially inhomogeneous metal-insulator mixed state.

The theory of electron?phonon superconductivity: does retardation really lead to a small Coulomb pseudopotential?

The theory of electron-phonon superconductivity depends on retardation drastically reducing the effects of the strong Coulomb repulsion. The standard theory only treats the lowest order diagram, which is an uncontrolled approximation. We study retardation in the Hubbard-Holstein model in a controlled way using perturbation theory and dynamical mean-field theory. We calculate second order results for the pseudopotential μ* analytically and demonstrate the validity up to intermediate couplings by comparison with non-perturbative results. Retardation effects are still operative, but less efficient, leading to somewhat larger values of μ*. Therefore, our theory can help in the understanding of situations where the standard theory yields overestimates for T(c).

Quantitative reliability study of the Migdal-Eliashberg theory for strong electron-phonon coupling in superconductors

We reassess the validity of the Migdal-Eliashberg (ME) theory for coupled electron-phonon systems for large couplings

Retardation effects and the Coulomb pseudopotential in the theory of superconductivity

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Microscopic Theory of Resistive Switching in Ordered Insulators: Electronic versus Thermal Mechanisms

. Although model calculations have found that the ME theory breaks down for

Energy dissipation in a dc-field-driven electron lattice coupled to fermion baths

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Mapping of strongly correlated steady-state nonequilibrium system to an effective equilibrium

, it is routinely applied for

Quantum simulation of many-body effects in steady-state nonequilibrium : Electron-phonon coupling in quantum dots

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Nonequilibrium mean-field theory of resistive phase transitions

to strong-coupling superconductors. To resolve this discrepancy, it is important to distinguish between bare parameters, used as input in models, and effective parameters, derived from experiments. We show explicitly that ME gives accurate results for the critical temperature and the spectral gap for large effective

Analytic understanding of resistive switching in ordered solids

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