Pulsed-THz Characterization of Hg-Based, High-Temperature Superconductors
Cross, X.L.
Zheng, X.
Cunningham, P.D.
Hayden, L.M.
Chromik, S.
Sojkova, M.
Strbik, V.
Odier, P.
Sobolewski, R.
Univ. of Rochester, Rochester, NY, USA;
This paper appears in: Applied Superconductivity, IEEE Transactions on
Publication Date: June 2009
Volume: 19,
Issue: 3, Part 3
On page(s): 3614-3617
ISSN: 1051-8223
INSPEC Accession Number: 10782316
Digital Object Identifier: 10.1109/TASC.2009.2018122
First Published: 2009-06-30
Current Version Published: 2009-07-17
Abstract
We report on ultrafast THz-pulse time-domain spectroscopy (TDS) and femtosecond optical-pump THz-probe (OPTP) studies of Hg-Ba-Ca-Cu-O (HBCCO) high-temperature, superconducting thin films. Our 500-nm-thick films were prepared by rf-magnetron sputtering of Re-Ba-Ca-Cu-O precursor films, followed by an ex-situ, high-temperature mercuration process. The resulting films were c axis oriented with a predominant Hg-1212 (plus some Hg-1223) phase. Their transition temperature Tc had an onset at 122 K and zero resistance at 110 K. The THz TDS measurements demonstrated a sharp drop in the transmitted THz signal when the sample temperature was decreased below Tc, which we directly related to a change in the imaginary component of the film complex conductivity. Simultaneously, the peak of the temperature-dependent real part of the conductivity was shifted toward lower frequencies at lower temperatures. The time-resolved OPTP spectroscopy experiments showed that the quasiparticle relaxation process exhibited an intrinsic single-picosecond dynamics with no phonon bottleneck, which is a unique feature among superconductors and makes the HBCCO material promising for ultrafast radiation detector applications.
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