Microwave surface impedance measurements of TlxPb1−xTe: A proposed negative-U induced superconductor
P. J. Baker, R. J. Ormeno, C. E. Gough, Y. Matsushita, I. R. Fisher
DOI 10.1103/PhysRevB.81.064506 · Physical Review B
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Abstract
The microwave surface impedance of the proposed negative-U induced superconductor Tl(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, Rs and Xs at low temperatures showed no significant power-law T dependence. From the low-temperature values of Xs, we extracted λ(0)=1.9±0.2 μm, in good agreement with rigid-band model predictions. A coherence peak was observed in σ1 below Tc consistent with BCS predictions. However, the observed temperature dependence of the superfluid fraction [λ(0)/λ(T)]2 fitted BCS predictions best if a somewhat larger value of λ(0)=2.7 μm 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 Bc3 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 Bc3 transition are strongly suggestive of conventional s-wave superconductivity.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| TlxPb1-xTe Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 1.4 | Pressure not reported | unknown |
| Tl0.014Pb0.986Te Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 1.4 | Pressure not reported | unknown |
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