Two-vison Gap in Chua-Yao-Fiette Model

We provide the programs created to find the two-vison gap in the Chua-Yao-Fiette (CYF) model, used in the results from "Visons in Kitaev Spin Liquids with Majorana Fermi Surfaces". The CYF is a "Kitaev-type" model in which spin-3/2 live in vertices of a Kagome Lattice. It supports Majorana fermions spectrum that, for some values of the Hamiltonian parameters, can present a Fermi surface. It also supports Z_2 vortices (visons) excitations, that can be created by changing the flux on specified plaquettes. The two-vison gap in the CYF model is calculated in two manners, as in the provided codes. First we perfrom numerical calculations: exact diagonalization on finite-size lattices. Then, we do analytical calculations on the thermodynamic limit, as described in the text of "Visons in Kitaev Spin Liquids with Majorana Fermi Surfaces".