Abstract
The Schawlow-Devlin self-inductance method of direct measurement of the penetration depth has been adapted for layered superconductors, for which this method is especially suitable because the calibration procedure is very simple for them. The ratio of coherence length to mean free path ξ0/l within the layer is deduced from the penetration depth measured by the new method and the resistivity, and is found to be 0.14 for a pure crystal of 2H-NbSe2 with RRR of about 50. The effect of the CDW transition on the superconductivity in 2H-NbSe2 is investigated through the measurement of the penetration depth. In addition to pure crystals, some modified crystals are investigated where the CDW transition is suppressed. The London penetration depth λL(0) as well as the superconducting transition temperatureT c show a slight but apparent increase with decreasing CDW transition temperature T D of the samples. Both behaviors may be explained by a decrease in the reduction ofN(EF) due to the suppression of the CDW transition, whereN(E F) is the density of states at the Fermi energy. The result also suggests a systematic increase of the ratio of effective mass to electron densitym∥/n of the electron system with the suppression of the CDW transition.
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Takita, K., Masuda, K. Charge density wave transition and superconductivity in 2H-NbSe2. Direct measurement of the penetration depth in a layered superconductor. J Low Temp Phys 58, 127–142 (1985). https://doi.org/10.1007/BF00682569
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DOI: https://doi.org/10.1007/BF00682569