Spin liquid mediated RKKY interaction

TL;DR

This paper introduces a novel RKKY-type interaction mediated by spin liquids, which can induce nuclear spin orderings in insulators without requiring itinerant electrons, and explores its properties in a kagome antiferromagnet.

Contribution

It proposes and analyzes a new form of RKKY interaction mediated by spin liquids, extending the concept beyond fermionic systems and exploring its implications in a kagome antiferromagnet.

Findings

Certain nuclear spin orderings are energetically favored but unstable due to flat magnon bands.

Applying a magnetic field can gap out magnon modes, stabilizing some nuclear spin configurations.

The interaction exhibits unique phenomenology distinct from traditional RKKY interactions in metals.

Abstract

We propose an RKKY-type interaction that is mediated by a spin liquid. If a spin liquid ground state exists such an interaction could leave a fingerprint by ordering underlying localized moments such as nuclear spins. This interaction has a unique phenomenology that is distinct from the RKKY interaction found in fermionic systems; most notably the lack of a Fermi surface and absence of the requirement for itinerant electrons, since most spin liquids are insulators. As a working example we investigate the two-dimensional spin-1/2 kagome antiferromagnet (KAFM), although the treatment remains general and can be extended to other spin liquids and dimensions. We find that several different nuclear spin orderings minimize the RKKY-type energy induced by the KAFM but are unstable due to a zero-energy flat magnon band. Despite this we show that a small magnetic field is able to gap out this magnon spectrum for some of the orderings resulting in an intricate nuclear magnetism.