Schwinger boson study of superconductivity mediated by antiferromagnetic spin-fluctuations

TL;DR

This paper investigates how spin-fluctuations in antiferromagnetic insulators can mediate superconductivity in adjacent metals, showing that frustration and phase transitions can enhance the critical temperature.

Contribution

It introduces a model combining Schwinger bosons and spin-fluctuations to analyze superconductivity mediated by frustrated antiferromagnetic phases.

Findings

Superconducting critical temperature increases with magnetic frustration.

Stripe phase antiferromagnetism can also mediate superconductivity.

Approaching the Néel phase transition further boosts the critical temperature.

Abstract

We study superconductivity in a normal metal, arising from effective electron-electron interactions mediated by spin-fluctuations in a neighboring antiferromagnetic insulator. Introducing a frustrating next-nearest neighbor interaction in a N\'eel antiferromagnet with an uncompensated interface, the superconducting critical temperature is found to be enhanced as the frustration is increased. Further, for sufficiently large next-nearest neighbor interaction, the antiferromagnet is driven into a stripe phase, which can also give rise to attractive electron-electron interactions. For the stripe phase, as previously reported for the N\'eel phase, the superconducting critical temperature is found to be amplified for an uncompensated interface where the normal metal conduction electrons are coupled to only one of the two sublattices of the magnet. The superconducting critical temperature arising from fluctuations in the stripe phase antiferromagnet can be further enhanced by approaching the transition back to the N\'eel phase.