Physical states and finite-size effects in Kitaev's honeycomb model: Bond disorder, spin excitations, and NMR lineshape

2015/02/28 by Fabian Zschocke, Matthias Vojta · 1 citation
Physics and Astronomy · #cond-mat.str-el #cond-mat.stat-mech

paper · pdf · doi:10.1103/physrevb.92.014403

published as Phys. Rev. B 92, 014403 (2015) · 13 pages, 10 figs; (v2) final version as published

arxiv created 2015/07/07 · arxiv updated 2015/07/08

Abstract

Kitaev's compass model on the honeycomb lattice realizes a spin liquid whose emergent excitations are dispersive Majorana fermions and static Z₂ gauge fluxes. We discuss the proper selection of physical states for finite-size simulations in the Majorana representation, based on a recent paper by Pedrocchi, Chesi, and Loss [Phys. Rev. B 84, 165414 (2011)]. Certain physical observables acquire large finite-size effects, in particular if the ground state is not fermion-free, which we prove to generally apply to the system in the gapless phase and with periodic boundary conditions. To illustrate our findings, we compute the static and dynamic spin susceptibilities for finite-size systems. Specifically, we consider random-bond disorder (which preserves the solubility of the model), calculate the distribution of local flux gaps, and extract the NMR lineshape. We also predict a transition to a random-flux state with increasing disorder.

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• Exact Organization of Density Matrices and Entanglement Structure in the Kitaev Spin Liquid

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