TY - ABST AU - Beck, Matthias AU - Leiderer, Paul AU - Kabanov, Viktor V. AU - Gol'tsman, Gregory AU - Helm, Manfred AU - Demsar, Jure PY - 2012 DA - 2012// TI - Energy-gap dynamics of a superconductor NbN studied by time-resolved terahertz spectroscopy T2 - INIS BT - INIS SP - 1 EP - 3 VL - 45 IS - 12 KW - NbN energy gap AB - Using time-resolved terahertz (THz) spectroscopy we performed direct studies of the photoinduced suppression and recovery of the SC gap in a conventional SC NbN. Both processes are found to be strongly temperature and excitation density dependent. The analysis of the data with the established phenomenological Rothwarf-Taylor model enabled us to determine the important microscopic constants: the Cooper pair-breaking rate via phonon absorption and the bare quasiparticle recombination rate. From the latter we were able to extract the dimensionless electron-phonon coupling constant, λ=1.1±0.1, in excellent agreement with theoretical estimates. The technique also allowed us to determine the absorbed energy required to suppress SC, which in NbN equals the thermodynamic condensation energy (in cuprates the two differ by an order of magnitude). Finally, we present the first studies of dynamics following resonant excitation with intense narrow band THz pulses tuned to above and below the superconducting gap. These suggest an additional process, particularly pronounced near Tc, that could be attributed to amplification of SC via effective quasiparticle cooling. UR - https://inis.iaea.org/search/search.aspx?orig_q=RN:45029889 N1 - exported from refbase (https://db.rplab.ru/refbase/show.php?record=1383), last updated on Thu, 13 May 2021 19:23:56 -0500 ID - Beck_etal2012 ER -