Visons em líquidos de Spin de Kitaev com superfícies de Fermi de Majoranas

Abstract

The Kitaev honeycomb model is an exactly solvable model that has a spin liquid ground state. It can have gapped or gapless excitations from Majorana fermions and vortices of a Z2 gauge field, also known as visons, which are always gapped. The energy to create a pair of visons has always been calculated numerically in finite-size lattices, but recently, an analytical expression valid in the thermodynamic limit was derived using Green’s function methods. An analytical method might be interesting for, when the Majoranas dispersion is gapless, the finite-size effects are stronger and might spoil extrapolations of the numerical vison gaps to the thermodynamic limit. In this work, we compare both methods to calculate the vison gap in the Kitaev model and generalize them to another model of spins 3 2 in the kagome lattice, in which Majorana fermions form a Fermi surface. We find a regime in which the vison gap decreases with the size of the Fermi surface.