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arXiv 1603.03354cond-mat.mes-hallcond-mat.supr-con
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与超导体耦合的正常层中的硬能隙

Hard gap in a normal layer coupled to a superconductor

Christopher R. Reeg, Dmitrii L. Maslov

摘要:

近年来,在工程拓扑超导体的背景下,在与常规超导体接触放置的正常层的激发光谱中诱导相当大的间隙的能力变得越来越重要。邻近效应的准经典理论表明,在超导体/正常界面处的Andreev反射在金属中引起非零的配对振幅,但不赋予它一个间隙。相反,当正常层是原子级薄时,库珀对的隧穿引起可以与超导体的体隙一样大的激发隙。我们研究如何这两个看似不同的观点的邻近效应演变成另一个正常层的厚度发生变化。我们表明,一个完全量子力学处理的问题预测,诱导间隙总是有限的,但下降的正常层,$d$的厚度。如果$d$小于某个交叉尺度,该交叉尺度远大于费米波长,则感生带隙与体带隙相当。因此,在比费米波长厚得多的正常层中可以诱导相当大的激发间隙。

英文摘要:

The ability to induce a sizable gap in the excitation spectrum of a normal layer placed in contact with a conventional superconductor has become increasingly important in recent years in the context of engineering a topological superconductor. The quasiclassical theory of the proximity effect shows that Andreev reflection at the superconductor/normal interface induces a nonzero pairing amplitude in the metal but does not endow it with a gap. Conversely, when the normal layer is atomically thin, the tunneling of Cooper pairs induces an excitation gap that can be as large as the bulk gap of the superconductor. We study how these two seemingly different views of the proximity effect evolve into one another as the thickness of the normal layer is changed. We show that a fully quantum-mechanical treatment of the problem predicts that the induced gap is always finite but falls off with the thickness of the normal layer, $d$. If $d$ is less than a certain crossover scale, which is much larger than the Fermi wavelength, the induced gap is comparable to the bulk gap. As a result, a sizable excitation gap can be induced in normal layers that are much thicker than the Fermi wavelength.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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