Small Superconductors—Introduction

Abstract

This article provides an overview of small superconductors, including some of the basic definitions, prominent characteristics, and important effects manifested by such materials. In particular, it discusses size effects, surface effects, electron-mean-free-path effects, phase slips, unusual vortex states, and proximity effects. The article first considers the two characteristic length scales of superconductors, namely the magnetic penetration depth and coherence length, before proceeding with an analysis of two size effects that account for how superconductivity responds when the bulk sample is made smaller and smaller in the nano range: the small size effects and the quantum size effects. It then examines other phenomena associated with small superconductors such as quantum fluctuations, Anderson limit, parity and shell effects, along with the behaviour of nanowires and ultra-thin fims. It also describes some of the experimental techniques commonly used in the synthesis of small superconductors.