Volume 101, Number 1, January 2013
|Number of page(s)||6|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||10 January 2013|
Theory of nonequilibrium dynamics of multiband superconductors
1 Max-Planck Institute for the Chemical Physics of Solids - D-01187 Dresden, Germany, EU
2 Theoretische Physik III, Ruhr-Universität Bochum - D-44780, Bochum, Germany, EU
3 Max-Planck-Institut für Festkörperforschung - D-70569 Stuttgart, Germany, EU
Received: 10 December 2012
Accepted: 18 December 2012
We study the nonequilibrium dynamics of multiband BCS superconductors subjected to ultrashort pump pulses. Using density-matrix theory, the time evolution of the Bogoliubov quasiparticle densities and the superconducting order parameters are computed as a function of pump pulse frequency, duration, and intensity. Focusing on two-band superconductors, we consider two different model systems. The first one, relevant for iron-based superconductors, describes two-band superconductors with a repulsive interband interaction V 12 which is much larger than the intraband pairing terms. The second model, relevant for MgB2, deals with the opposite limit where the intraband interactions are dominant and the interband pair scattering V 12 is weak but attractive. For ultrashort pump pulses, both of these models exhibit a nonadiabatic behavior which is characterized by oscillations of the superconducting order parameters. We find that for nonvanishing V 12, the superconducting gap on each band exhibits two oscillatory frequencies which are determined by the long-time asymptotic values of the gaps. The relative strength of these two frequency components depends sensitively on the magnitude of the interband interaction V 12.
PACS: 74.40.Gh – Nonequilibrium superconductivity / 78.47.J- – Ultrafast spectroscopy (<1 psec) / 78.20.Bh – Theory, models, and numerical simulation
© EPLA, 2013
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