Majorana mean-field theory with Z2 vortices: Electrical tests in the extended Kitaev model

Abstract

The Kitaev honeycomb model realizes a quantum spin liquid where spin degrees of freedom are fractionalized into itinerant Majorana fermions and localized vortices. The entanglement among these particles holds promise for executing fault-tolerant topological quantum computation. While several materials have been proposed to host a quantum spin liquid phase, concrete evidence confirming its existence remains elusive. To aid in identifying this phase, we propose an electrical test using the charge profile, offering a signature for the Z2 vortices in Kitaev materials. This study explores the electric charge response in Kitaev materials, considering a generalized spin model including Heisenberg, off-diagonal exchange interactions, and magnetic Zeeman field. Majorana mean-field theory is employed to analyze spin correlations around vortices, revealing spatial anisotropy in the charge distribution, quantified by the electric quadrupole moment. This mean-field approach remains exact in the pure Kitaev limit and captures the fundamental physics across the Kitaev spin liquid phase. The quadrupole-quadrupole interaction between distant vortices is shown to be either repulsive or attractive, depending on the parameters. We predict that electrically biased scanning probe tips can help create vortices at predetermined locations. The findings of our study pave the way for electrically manipulating Ising anyons in Kitaev spin liquids, offering a promising path for technological applications of Kitaev materials.