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arXiv · 0803.1185

The unusual thickness dependence of superconductivity in $α$-MoGe thin films

H. Tashiro·J. M. Graybeal·D. B. Tanner·E. J. Nicol·J. P. Carbotte·G. L. Carr
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Abstract

Thin films of $α$-MoGe show progressively reduced $T_{c}$'s as the thickness is decreased below 30 nm and the sheet resistance exceeds 100 $Ω/\Box$. We have performed far-infrared transmission and reflection measurements for a set of $α$-MoGe films to characterize this weakened superconducting state. Our results show the presence of an energy gap with ratio $2Δ_0/k_BT_{c} = 3.8 \pm 0.1$ in all films studied, slightly higher than the BCS value, even though the transition temperatures decrease significantly as film thickness is reduced. The material properties follow BCS-Eliashberg theory with a large residual scattering rate except that the coherence peak seen in the optical scattering rate is found to be strongly smeared out in the thinner superconducting samples. A peak in the optical mass renormalization at $2Δ_0$ is predicted and observed for the first time.

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H. Tashiro, J. M. Graybeal, D. B. Tanner, E. J. Nicol, J. P. Carbotte, G. L. Carr. 2008-03-07. The unusual thickness dependence of superconductivity in $α$-MoGe thin films. https://doi.org/10.1103/physrevb.78.014509

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