Title :
Femtosecond dynamics of quasi-particles in YBa2Cu3 O7-δ superconductor films
Author :
Han, S.G. ; Vardeny, Z.V. ; Symko, O.G. ; Koren, G.
Author_Institution :
Dept. of Phys., Utah Univ., Salt Lake City, UT, USA
fDate :
3/1/1991 12:00:00 AM
Abstract :
The transient electronic response of epitaxially grown YBa2 Cu3O7-δ superconductor thin films in the femtosecond time domain was investigated using transient photoinduced reflectivity (ΔR) with 60-fs time resolution. For temperatures T>Tc, only a bolometric signal was observed with ΔR>0. For T<Tc, ΔR<0 with a temperature-dependent rise time on the order of 300 fs was observed, followed by a relaxation (on the order of 3 ps) into a state with ΔR>0. The results for T<Tc are explained in terms of quasi-particle (QP) electronic response giving ΔR<0. Thus, the femtosecond rise time is interpreted as avalanche multiplication of QP across the gap 2Δ, and the subsequent picosecond relaxation is interpreted as QP recombination. The QP optical response is explained within the framework of the two-fluid model
Keywords :
barium compounds; high-temperature superconductors; reflectivity; superconducting thin films; time resolved spectra; yttrium compounds; 60 fs; YBa2Cu3O7-δ superconductor films; avalanche multiplication; bolometric signal; femtosecond time domain; high temperature superconductor; picosecond relaxation; quasi-particles; temperature-dependent rise time; transient electronic response; transient photoinduced reflectivity; two-fluid model; Optical films; Quadratic programming; Reflectivity; Signal resolution; Spontaneous emission; Superconducting epitaxial layers; Superconducting thin films; Temperature; Ultrafast electronics; Ultrafast optics;
Journal_Title :
Magnetics, IEEE Transactions on
