Flux mobility delocalization in the Kitaev spin ladder

TL;DR

This paper investigates how flux mobility influences delocalization in the Kitaev spin ladder, revealing that flux movement is essential for transport properties and delocalization, especially under magnetic fields.

Contribution

It demonstrates that flux mobility, rather than magnetic field alone, drives delocalization in the Kitaev spin ladder, using numerical methods to analyze transport and localization.

Findings

Flux mobility is necessary for delocalization.

Magnetic fields comparable to the flux gap induce flux mobility.

Finite dc transport coefficients are observed in the delocalized regime.

Abstract

We study the Kitaev spin-$1/2$ ladder, a model which exhibits self-localization due to fractionalization caused by exchange frustration. When a weak magnetic field is applied, the model is described by an effective fermionic Hamiltonian, with an additional time reversal symmetry breaking term. We show that this term alone is not capable of delocalizing the system but flux mobility is a prerequisite. For magnetic fields larger but comparable to the flux gap, fluxes become mobile and drive the system into a delocalized regime, featuring finite dc transport coefficients. Our findings are based on numerical techniques, exact diagonalization and dynamical quantum typicality, from which, we present results for the specific heat, the dynamical energy current correlation function, as well as the inverse participation ratio, contrasting the spin against the fermion representation. Implications of our results for two-dimensional extensions of the model will be speculated on.