Charge density wave transition and superconductivity in 2H-NbSe2. Direct measurement of the penetration depth in a layered superconductor
Charge density wave transition and superconductivity in 2H-NbSe2. Direct measurement of the penetration depth in a layered superconductor
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2H-NbSe2 中的电荷密度波跃迁和超导性。
DOI：
10.1007/bf00682569
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发表时间：
1985
影响因子：
2
通讯作者：
K. Masuda
中科院分区：
文献类型：
--
作者：
K. Takita;K. Masuda
直接测量穿透深度的 Schawlow-Devlin 自感法已适用于层状超导体，该方法特别适合层状超导体，因为其校准过程非常简单。根据新方法测量的穿透深度和电阻率推导了层内相干长度与平均自由程的比值 ψ0/l，发现对于 RRR 约为 50 的 2H-NbSe2 纯晶体，该比值为 0.14。通过穿透深度的测量，研究了 CDW 跃迁对 2H-NbSe2 超导性的影响。除了纯晶体之外，还研究了一些 CDW 跃迁受到抑制的改性晶体。随着样品 CDW 转变温度 TD 的降低，伦敦穿透深度 λL(0) 以及超导转变温度 Tc 显示出轻微但明显的增加。这两种行为都可以通过 CDW 跃迁的抑制导致 N(EF) 的还原减少来解释，其中 N(EF) 是费米能级下的态密度。结果还表明，随着 CDW 跃迁的抑制，电子系统的有效质量与电子密度 m∥/n 的比率系统性增加。
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 temperatureTc show a slight but apparent increase with decreasing CDW transition temperature TD 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(EF) 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.