Macroscopic Degeneracy and Emergent Frustration in a Honeycomb Lattice Magnet

TL;DR

This paper explores how competing interactions in a honeycomb lattice lead to emergent geometrical frustration and macroscopic degeneracy, revealing novel phenomena in itinerant electron systems.

Contribution

It introduces a hybrid computational approach to uncover emergent frustration and degeneracy in a honeycomb lattice with itinerant and localized spins.

Findings

Formation of a frustrated triangular lattice of hexagons

Existence of a stable dimerized ground state with macroscopic degeneracy

Emergent geometrical frustration in a non-frustrated lattice

Abstract

Using a hybrid method based on fermionic diagonalization and classical Monte Carlo, we investigate the interplay between itinerant and localized spins, with competing double- and super-exchange interactions, on a honeycomb lattice. For moderate superexchange, a geometrically frustrated triangular lattice of hexagons forms spontaneously. For slightly larger superexchange a dimerized groundstate is stable that has macroscopic degeneracy. The presence of these states on a non-frustrated honeycomb lattice highlights a novel phenomenon in this itinerant electron system: emergent geometrical frustration and degeneracy.