Emergent Quantum Coherence from Instabilities of a Perturbed Fractionalized Spin Liquid

TL;DR

This paper explores how perturbations induce emergent quantum coherence and novel orders in topologically ordered spin liquids, revealing new fractionalized states and potential experimental signatures like fractional Josephson oscillations.

Contribution

It provides a quasi-exact realization of emergent orders in perturbed Kitaev spin liquids and links these phenomena to observable effects such as fractional Josephson oscillations.

Findings

Partial topological order coexists with excitonic orders under perturbations.

Identification of strange metallic features like nodal spin-metals and Luttinger surfaces.

Proposal of Josephson-junction arrays exhibiting fractional Josephson oscillations.

Abstract

Effects of perturbations on topologically ordered (TO) states with fractionalized excitations is very intriguing. While small perturbations are not expected to affect a robust TO, sizable perturbations must lead to onset of novel routes to order(s). Observability of such emergent orders in real condensed matter systems continues to be an open issue of paramount interest. Here, we detail how a featureless Kitaev spin liquid with rigorous TO gives way to partial topological ordered state(s) coexisting with a wide staircase of novel `excitonic' orders of fractionalized entities in a Zeeman field. We provide quasi-exact and novel realization for a range of strange features, from nodal spin-metals, fractionalization in selective-Mott states, to Luttinger surfaces and hidden coherence, all characteristics of the influential resonating- valence-bond as well as fractionalized-Fermi-Liquid views in the context of strange metals. As a novel application, we show how Josephson-junction array may exhibit fractional Josephson oscillations upon flux tuning as a particularly novel manifestation of emergent quantum coherence.