Spin and charge dynamics of photogenerated quasiparticles in superconducting NbTiN

ORAL

Abstract

We use time-resolved broadband far-infrared spectroscopy to study the dynamics of photogenerated quasiparticles in superconducting Nb$_{0.5}$Ti$_{0.5}$N. The pump-probe measurements used picosecond pulses from a near-infrared Ti:sapphire laser as a pump and subnanosecond pulses of infrared synchrotron radiation as the probe. Measurements were done as a function of fluence and applied magnetic field. The measurements were performed at the National Synchrotron Light Source, Brookhaven National Laboratory.; We report the photoinduced far-infrared transmission at 2 K for two different field orientations: perpendicular and parallel to the Nb$_{0.5} $Ti$_{0.5}$N film. The decay does not follow a simple exponential. We observed a linear scaling behavior between the number of photoexcited quasiparcles and the relaxation rate. In addition, the relaxation rate decreases linearly with magnetic field, attributed to spin polarization of the quasiparticles in the field.

*The research has been supported by the DOE through grant DE-FG02-02ER45984 at Florida and contract DE-AC02-98CH10886 at BNL.

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Authors

  • J. Hwang

    • University of Florida
    • Department of Physics, University of Florida

  • X. Xi

    • University of Florida
    • Department of Physics, University of Florida

  • Dave H. Reitze

    • University of Florida
    • Department of Physics, University of Florida
    • Physics Dept. University of Florida

  • C.J. Stanton

    • Univ. of FL
    • University of Florida
    • Department of Physics, University of Florida

  • David B. Tanner

    • University of Florida
    • Department of Physics, University of Florida
    • UFL, phys dept

  • G.L. Carr

    • Brookhaven National Laboratory
    • NSLS, Brookhaven National Laboratory
    • NSLS, Brookhaven National Laboratory, Upton, NY
    • NSLS, Brookhaven National Lab