Amperean Pairing Instability in the U(1) Spin Liquid State with Fermi Surface and Application to $\kappa-(BEDT-TTF)_2 Cu_2 (CN)_3$

TL;DR

This paper proposes an Amperean pairing state in a U(1) spin liquid with a Fermi surface, explaining experimental observations in the organic compound $2-(BEDT-TTF)_2 Cu_2 (CN)_3$ through gauge field-mediated spinon interactions.

Contribution

It introduces a novel Amperean pairing mechanism for spinons in a U(1) spin liquid, linking gauge interactions to observable low-temperature phenomena.

Findings

The proposed pairing state explains experimental low-temperature behaviors.

Testable predictions are made for future experiments.

The mechanism highlights the role of gauge fields in quantum spin liquids.

Abstract

Recent experiments on the organic compound $\kappa-(BEDT-TTF)_2 Cu_2 (CN)_3$ raise the possibility that the system may be described as a quantum spin liquid. Here we propose a pairing state caused by the `Amperean' attractive interaction between spinons on a Fermi surface mediated by the U(1) gauge field. We show that this state can explain many of the observed low temperature phenomena and discuss testable consequences.