Weyl spin liquids

TL;DR

This paper explores the fractionalization of magnetic moments in 3D Kitaev models, revealing a Weyl spin liquid state with topological features and potential experimental signatures.

Contribution

It demonstrates that Majorana fermions in a 3D Kitaev model form a Weyl superconductor, introducing the concept of a Weyl spin liquid in a real material.

Findings

Majorana fermions form a Weyl superconductor in the hyperhoneycomb Kitaev model

Identification of topologically protected bulk and surface features of the Weyl spin liquid

Prediction of thermodynamic and transport signatures of the Weyl spin liquid

Abstract

The fractionalization of quantum numbers in interacting quantum-many body systems is a central motif in condensed matter physics with prominent examples including the fractionalization of the electron in quantum Hall liquids or the emergence of magnetic monopoles in spin-ice materials. Here we discuss the fractionalization of magnetic moments in three-dimensional Kitaev models into Majorana fermions (and a $\mathbb Z_2$ gauge field) and their emergent collective behavior. We analytically demonstrate that the Majorana fermions form a Weyl superconductor for the Kitaev model on the recently synthesized hyperhoneycomb structure of $\beta$-Li$_2$IrO$_3$ when applying a magnetic field. We characterize the topologically protected bulk and surface features of this state, which we dub a Weyl spin liquid, including thermodynamic and transport signatures.