Zero energy Majorana modes in spin ladders and a possible realization of the Kitaev model

TL;DR

This paper demonstrates the emergence of zero-energy Majorana modes in spin ladders with disordered potentials and proposes a new realization of the Kitaev model where Majorana fermions can move in multiple dimensions.

Contribution

It introduces a mechanism for Majorana modes in disordered spin ladders and suggests a generalized Kitaev model with multi-dimensional Majorana propagation.

Findings

Disordered ionic potentials create dimerized islands in spin liquids.

Boundary between phases hosts localized Majorana fermions.

Proposes a multi-dimensional Majorana propagation in a generalized Kitaev model.

Abstract

We show that in double-chain Mott insulators (ladders), disordered alternating ionic potentials may locally destroy coherence of magnetic excitations and lead to the appearance of spontaneously dimerized islands inside the Haldane spin-liquid phase. We argue that a boundary between the dimerized and Haldane phases of a spin-1/2 ladder supports a localized zero-energy Majorana fermion mode. Based on these findings we suggest a realization of a generalized Kitaev model where Majorana fermions can propagate in more than one dimension.