Microwave surface impedance measurements of T1(x)Pb(1-x)Te: A proposed negative-U induced superconductor

PJ Baker, RJ Ormeno, Colin Gough, Y Matsushita, IR Fisher

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The microwave surface impedance of the proposed negative-U induced superconductor T1(1.4%) PbTe has been measured for a number of single crystals at several frequencies from 4.5 to 15.2 GHz in both the zero-field and mixed superconducting states. For crystals with the best-quality surfaces, R-s and X-s at low temperatures showed no significant power-law T dependence. From the low-temperature values of Xs, we extracted lambda(0) = 1.9 +/- 0.2 mu m, in good agreement with rigid- band model predictions. A coherence peak was observed in sigma(1) below T-c consistent with BCS predictions. However, the observed temperature dependence of the superfluid fraction [lambda(0)/lambda(T)](2) fitted BCS predictions best if a somewhat larger value of lambda(0) = 2.7 mu m was assumed, which may be associated with remanent surface defects in even our best sample. In addition to investigating the field dependence of the microwave properties in the mixed state, a B-c3 transition region was observed. The absence of a significant power-law temperature dependence at low temperatures in our best sample and the observation of a B-c3 transition are strongly suggestive of conventional s-wave superconductivity.
Original languageEnglish
Article number064506
Pages (from-to)064506
Number of pages1
JournalPhysical Review B
Issue number6
Publication statusPublished - 1 Feb 2010


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