Submillimeter surface impedance and relaxation: A case study of quasi-two-dimensional YBa2Cu3Ox |
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Authors: | J Halbritter |
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Affiliation: | (1) Institut für Materialund Festkörperforschung I, Kernforschungszentrum Karlsruhe GmbH, Postfach 3640, 7500 Karlsruhe 1, Germany |
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Abstract: | Surface impedance measurements in the normal and superconducting state are an excellent method to study the conduction electron dynamics in metals. This holds especially in the relaxation range, i.e., for distances traveled in one r.f. periods=
F/ ( f is the Fermi velocity) being smaller or of the order of the penetration depth and mean free pathl. For materials with
F<-107 cm/sec the relaxation range is easily accessible forf>0.1 THz. Then, in the normal state, relaxation defines the surface impedance with a penetration depth approaching the London penetration depth L, andR![ap](/content/jv46h20211955v66/xxlarge8776.gif)
0 l/2 as surface resistance allowing a measure of L and relaxation time (T, ). In the superconducting state the photon interaction scales with
F/ L=l/ (
f is the dimension of Cooper pairs for l![rarr](/content/jv46h20211955v66/xxlarge8594.gif) ) and causes at low frequencies an absorption rate growing with , which is decreasing with
F/l. The rate increase proportional to turns to a decrease above 0.1 THz, being accompanied by a decrease of with frequency which is stronger for large and small
F/l. These characteristic dependences allow a measurement of material parameters, anisotropy, and dynamics of electrons. To evaluate the consequences of theâ, b, and -direction anisotropy, the integral kernels for normal and superconducting surface impedances in its nonintegrated, angle-dependent form are presented, analyzed, and compared with impedance measurements above 0.1 THz of YBa2Cu3Ox. |
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Keywords: | Superconductors surface impedance two-dimensionality |
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