Interplay between pairing and exchange in small metallic dots

TL;DR

This paper investigates how mesoscopic fluctuations influence the competition between exchange and pairing interactions in ultrasmall metallic dots, revealing universal features and sample-to-sample variations in ground state spin and pairing.

Contribution

It provides new insights into the role of mesoscopic fluctuations on spin states and pairing in small metallic systems with large level spacing.

Findings

Non-zero spin ground states occur with non-vanishing probability due to fluctuations.

Universal features relate to level statistics and interactions.

Sample-to-sample fluctuations significantly affect pairing strength.

Abstract

We study the effects of the mesoscopic fluctuations on the competition between exchange and pairing interactions in ultrasmall metallic dots when the mean level spacing is comparable or larger than the BCS pairing energy. Due to mesoscopic fluctuations, the probability to have a non-zero spin ground state may be non-vanishing and shows universal features related to both level statistics and interaction. Sample to sample fluctuations of the renormalized pairing are enlightened.