Possible electronic shell structure of nanoscale superconductors

2019-11-09 00:36:55

effects electron density gap canonical

责任者: Tanaka, K.;Marsiglio, F. 单位: Dept. of Phys., Alberta Univ., Edmonton, Alta., Canada 来源出处: Physics Letters A(Phys. Lett. A (Netherlands)),2000/01/17,265(1-2):133-8 摘要: Motivated by recent experiments on Al nanoparticles, we have studied the effects of fixed electron number and small size in nanoscale superconductors, by applying the canonical BCS theory for the attractive Hubbard model in two and three dimensions. As observed in the experiments, a negative `gap in particles with an odd number of electrons emerges naturally in the canonical scheme. For particles with an even number of electrons, the canonical energy gap exhibits shell structure as a function of electron density or system size in the weak-coupling regime: the gap is particularly large for `magic numbers of electrons for a given system size or of atoms for a fixed electron density. The grand canonical BCS method essentially misses this feature. Possible experimental methods for observing such shell effects are discussed 关键词: BCS theory;electron density;Hubbard model;nanostructured materials;superconducting energy gap;electronic shell structure;nanoscale superconductors;Al nanoparticles;fixed electron number effects;small size effects;2D-attractive Hubbard model;3D-attractive Hubbard model;canonical energy gap;weak-coupling regime;magic numbers;electron density;grand canonical BCS theory;Al