Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 15: Superconductivity: Poster Session

TT 15.26: Poster

Tuesday, February 26, 2008, 14:00–18:00, Poster B

Pump-probe spectra and nonlinear dynamics of BCS superconductors — Thomas Papenkort¹, •Norina Richter¹, Vollrath Martin Axt², and Tilmann Kuhn¹ — ¹Institut für Festkörpertheorie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster — ²Institut für Theoretische Physik III, Universität Bayreuth, 95440 Bayreuth

We present numerical calculations of the reaction of a BCS superconductor to short laser pulses. Starting from the BCS ground state, a laser pulse decreases the modulus of the order parameter, |Δ|. The intensity dependence of this shift depends strongly on the temporal width of the laser pulse. It may be measured using pump-probe spectroscopy: |Δ| ist directly linked to the energy gap of the superconductor which in turn is clearly visible in the absorption spectra. If the probe pulse precedes the pump pulse, an oscillation is superimposed on the spectrum and both the gap before and after the pump pulse can be seen. After very short pump pulses |Δ| does not remain constant but instead oscillates. The time dependence of this oscillation is in very good agreement with exact results obtained for the dynamics of a BCS system without external driving following a sudden change into a nonequilibrium state.