LEVEL STATISTICS AND PARITY EFFECT ON SMALL SUPERCONDUCTING SYSTEMS

• 来源期刊: 中国物理（英文版）
• 关键词: superconductivity level statistics parity effect
• 年，卷（期）: 2001,（12）
• 页码范围: 1149-1153
• 页数: 5页
• 语种: 英文

摘要

In this paper we have calculated the variations of the gap △'(0, d) and transition temperature Tc' in small metallic grains as functions of grain size (or the level spacing d between discrete electronic states) for the cases of odd and even numbers of electrons by applying the random matrix theory to the mean field theory. We find the presence of enhancement of superconductivity and critical dc, where the superconductivity of small grains breaks down. This agrees with Anderson's prediction (1959 J. Phys. Chem. Solids 11 28). We find that in the grains, as the size is lowered,the transition temperature Tc' decreases and A'(O, d)/kBTc' ≤πe-γ in odd numbers of electrons, and for Gaussian orthogonal and unitary ensembles in some regimes △'(0, d)/kBTc' ＞πe-γ in even numbers of electrons.