Superconductor-Insulator Transitions and Insulators with Localized Pairs

TL;DR

This paper investigates the superconductor-insulator transition in amorphous In--O films and explores the role of localized Cooper pairs, revealing complex transport mechanisms and challenging existing scaling theories.

Contribution

It presents experimental evidence on the behavior of resistance near the transition and discusses the potential for pair hopping in insulating states with localized pairs.

Findings

Resistance derivative at critical field is non-zero at zero temperature.

Evidence of a shunting conduction mechanism below 0.1 K.

Discussion of pair hopping as a transport process.

Abstract

Two experiments are described which are related to the problem of localized Cooper pairs. Magnetic-field-tuned superconductor-insulator transition was studied in amorphous In--O films with onset of the superconducting transition in zero field near 2 K. Experiments performed in the temperature range T>0.3 K indicate that at the critical field, B=B_c, the first derivative of the resistance dR/dT is non-zero at T=0 and hence the scaling relations should be written in more general form. Study of the magnetotransport of high-resistance metastable alloy Cd-Sb on the insulating side of the superconductor-insulator transition revealed below 0.1 K a shunting condiction mechanism in addition to usual one-particle hopping. Possibility of pair hopping is discussed.