Residual and intrinsic surface resistance ofYBa2Cu3O7−δ
| Autor: | Herman J. Fink |
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| Rok vydání: | 1998 |
| Předmět: | |
| Zdroj: | Physical Review B. 58:9415-9420 |
| ISSN: | 1095-3795 0163-1829 |
| DOI: | 10.1103/physrevb.58.9415 |
| Popis: | A simple model is proposed which describes correctly the essential traits of the microwave surface resistance ${R}_{s}$ of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ above and below the transition temperature ${T}_{c}.$ One of the key features is an electron scattering rate, which is the sum of a temperature- ($T$-) independent term and one that obeys the Gr\"uneisen $T$ dependence, and is carried over unchanged from the normal to the superconducting state. Furthermore, the $T$ dependence of the quasiparticles is related to the empirical penetration depth, $\ensuremath{\lambda}(T).$ We find that ${R}_{s}(T)$ depends linearly on $T$ at low temperatures, which is a consequence of a predominantly constant elastic electron scattering rate and a linear $T$ dependent $[\ensuremath{\lambda}(T){]}^{\ensuremath{-}2}$ in the $\mathrm{ab}$ plane as $\stackrel{\ensuremath{\rightarrow}}{T}0\mathrm{K}.$ We confirm previous experiments indicating that a maximum and a minimum of ${R}_{s}(T)$ between absolute zero and ${T}_{c}$ is the signature of a clean specimen, corresponding to a small residual resistivity. Increasing the residual resistivity suppresses the peak of ${R}_{s}(T)$ and lowers the surface resistance. The real part of the conductivity ${\ensuremath{\sigma}}^{\ensuremath{'}}$ of a relatively clean specimen shows a distinct peak below ${T}_{c}$ which is caused by the Gr\"uneisen $T$ dependent intrinsic resistivity, together with a gradual freezing out of the quasiparticles, and a remaining residual resistivity as $\stackrel{\ensuremath{\rightarrow}}{T}0\mathrm{K}.$ The slopes of ${R}_{s}(T)$ and of ${\ensuremath{\sigma}}^{\ensuremath{'}}(T)$ are discontinuous at ${T}_{c}.$ Increasing the frequency and/or the residual resistivity decreases the peak of ${\ensuremath{\sigma}}^{\ensuremath{'}}$ and shifts it to higher temperatures. The slope of ${R}_{s}^{2}(T)$ just above ${T}_{c}$ is linear and proportional to the Debye temperature. |
| Databáze: | OpenAIRE |
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