395 research outputs found
Floquet States
Full text linkQuantum systems driven by a time-periodic field are a platform of condensed
matter physics where effective (quasi)stationary states, termed "Floquet
states", can emerge with external-field-dressed quasiparticles during driving.
They appear, for example, as a prethermal intermediate state in isolated driven
quantum systems or as a nonequilibrium steady state in driven open quantum
systems coupled to environment. Floquet states may have various intriguing
physical properties, some of which can be drastically different from those of
the original undriven systems in equilibrium. In this article, we review
fundamental aspects of Floquet states, and discuss recent topics and
applications of Floquet states in condensed matter physics.Comment: 12 pages, 6 figures, prepared for Encyclopedia of Condensed Matter
Physics, 2nd edition; minor revision is mad
Photoinduced insulator-metal transition in correlated electrons -- a Floquet analysis with the dynamical mean-field theory
Full text linkIn order to investigate photoinduced insulator-metal transitions observed in
correlated electron systems, we propose a new theoretical method, where we
combine a Floquet-matrix method for AC-driven systems with the dynamical
mean-field theory. The method can treat nonequilibrium steady states exactly
beyond the linear-response regime. We have applied the method to the
Falicov-Kimball model coupled to AC electric fields, and numerically obtained
the spectral function, the nonequilibrium distribution function and the
current-voltage characteristic. The results show that intense AC fields indeed
drive Mott-like insulating states into photoinduced metallic states in a
nonlinear way.Comment: 4 pages, 3 figures, Proceedings of LT2
Repulsion-to-attraction transition in correlated electron systems triggered by a monocycle pulse
Full text linkWe study the time evolution of the Hubbard model driven by a half-cycle or
monocycle pulsed electric field F(t) using the nonequilibrium dynamical
mean-field theory. We find that for properly chosen pulse shapes the
electron-electron interaction can be effectively and permanently switched from
repulsive to attractive if there is no energy dissipation. The physics behind
the interaction conversion is a nonadiabatic shift of the population
in momentum space. When , the shifted population relaxes to a
negative-temperature state, which leads to the interaction switching. Due to
electron correlation effects deviates from the dynamical phase
, which enables the seemingly counterintuitive
repulsion-to-attraction transition by a monocycle pulse with .Comment: 6 pages, 6 figure
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