Chiral spin liquid instability of the Kitaev honeycomb model with crystallographic defects

TL;DR

Introducing lattice defects into the Kitaev honeycomb model induces a finite-temperature phase transition to a non-Abelian chiral spin liquid, driven by defect-mediated interactions and fermionic fluctuations.

Contribution

First demonstration that lattice defects in the Kitaev model can induce a topological phase transition to a chiral spin liquid.

Findings

Finite defect density leads to a phase transition at temperature ~2 times the defect density.

The chiral spin liquid exhibits scalar spin chirality and orbital magnetization peaking near defects.

Emergent long-range ferromagnetic interactions between defect chiralities are mediated by fermions.

Abstract

We study the spin-1/2 Kitaev honeycomb gapless spin liquid in the presence of Stone-Wales-type local lattice defects with odd-sided plaquettes. While the clean Kitaev model has no finite-temperature phase transitions, we find that introducing a finite defect density $n_d\approx 10^{-4}$--$10^{-2}$ produces a true phase transition with a sizeable $T_c \approx 2 n_d$ in units of the Kitaev exchange. The resulting non-Abelian chiral quantum spin liquid exhibits scalar spin chirality and electron orbital magnetization which peak near lattice defects. This disorder-driven instability relies on an emergent long range ferromagnetic interaction $r^{-\gamma}$ ($\gamma \approx 2.7$) between defect chiralities, mediated by the nearly-gapless fermions, with implications for topology generation in Dirac cones with fluctuating mass terms.