Phase transitions in individual sub-micrometre superconductors
Phase transitions in individual sub-micrometre superconductors
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DOI：
10.1038/36797
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发表时间：
1997-11-20
期刊：
影响因子：
64.8
通讯作者：
Peeters, FM
中科院分区：
文献类型：
--
作者：
Geim, AK;Grigorieva, IV;Peeters, FM
当一个超导体的尺寸变得与库珀对（超导的准粒子）相当时，它的性质就会发生根本性的变化。在磁场抑制超导性的情况下，这种限制的效果是很好理解的（这引起了所谓的相边界的Little-Parks振荡）（1-4）。但是，人们对小超导体在零电阻状态下会发生什么知之甚少，这无法通过电阻测量来探测。在这里，我们应用一种新的弹道霍尔磁力测量技术（5）来研究直径低至100 nm的单个超导盘的磁化。发现这些盘的超导状态与宏观和微观超导体都有质的不同，具有许多相变，其特征随尺寸和温度迅速变化。这种奇特的行为是由于库珀对运动的尺寸量子化和由此产生的超导玻色凝聚体在磁场中的离散状态之间的过渡。
The properties of a superconductor are expected to change radically when its size becomes comparable to that of the Cooper pairs, the quasiparticles responsible for superconductivity. The effect of such confinement is well understood for the case of the suppression of superconductivity by magnetic fields (which gives rise to so-called Little-Parks oscillations of the phase boundary)(1-4). But little is known about what happens in small superconductors in the zero-resistance state, which cannot be probed by resistance measurements. Here we apply a new technique of ballistic Hall magnetometry(5) to study the magnetization of individual superconducting discs of diameters down to 100 nm. The superconducting state of these discs is found to be qualitatively different from both macroscopic and microscopic(6) superconductors, with numerous phase transitions whose character changes rapidly with size and temperature. This exotic behaviour is due to size quantization of the Cooper-pair motion and resulting transitions between discrete states of the superconducting Bose condensate in a magnetic field.