Quantum gap and spin-wave excitations in the Kitaev model on a triangular lattice

TL;DR

This paper investigates how quantum fluctuations influence the emergence of a gap and the spin-wave spectrum in a frustrated triangular lattice magnet with Kitaev-like interactions, revealing a quantum order-by-disorder mechanism and emergent four-spin interactions.

Contribution

It demonstrates how quantum fluctuations lift degeneracy and generate a spin gap through an emergent four-spin interaction in a frustrated Kitaev model on a triangular lattice.

Findings

Quantum fluctuations lift classical degeneracy via order-by-disorder.

A spin gap emerges, shifting nodal lines to finite energies.

The ground state degeneracy is protected by a hidden symmetry.

Abstract

We study the effects of quantum fluctuations on the dynamical generation of a gap and on the evolution of the spin-wave spectra of a frustrated magnet on a triangular lattice with bond-dependent Ising couplings, analog of the Kitaev honeycomb model. The quantum fluctuations lift the subextensive degeneracy of the classical ground-state manifold by a quantum order-by-disorder mechanism. Nearest-neighbor chains remain decoupled and the surviving discrete degeneracy of the ground state is protected by a hidden model symmetry. We show how the four-spin interaction, emergent from the fluctuations, generates a spin gap shifting the nodal lines of the linear spin-wave spectrum to finite energies.