Ozer Mustafa M, Jia Yu, Zhang Zhenyu, Thompson James R, Weitering Hanno H
Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA.
Science. 2007 Jun 15;316(5831):1594-7. doi: 10.1126/science.1142159.
Quantum confinement of itinerant electrons in atomically smooth ultrathin lead films produces strong oscillations in the thickness-dependent film energy. By adding extra electrons via bismuth alloying, we showed that both the structural stability and the superconducting properties of such films can be tuned. The phase boundary (upper critical field) between the superconducting vortex state and the normal state indicates an anomalous suppression of superconducting order just below the critical temperature, Tc. This suppression varies systematically with the film thickness and the bismuth content and can be parametrized in terms of a characteristic temperature, Tc* (less than Tc), that is inversely proportional to the scattering mean free path. The results indicate that the isotropic nature of the superconductive pairing in bulk lead-bismuth alloys is altered in the quantum regime.
在原子级光滑的超薄铅膜中，巡游电子的量子限制会在与厚度相关的薄膜能量中产生强烈振荡。通过铋合金化添加额外电子，我们表明此类薄膜的结构稳定性和超导特性均可被调控。超导涡旋态与正常态之间的相边界（上临界场）表明，在临界温度(Tc)以下，超导序会出现反常抑制。这种抑制随薄膜厚度和铋含量系统性变化，并且可以用一个特征温度(Tc^*)（小于(Tc)）来参数化，该特征温度与散射平均自由程成反比。结果表明，体相铅铋合金中超导配对的各向同性本质在量子 regime 中发生了改变。
