Spin conductivity in two-dimensional Heisenberg model on Lieb lattice under magnetic field and spin-orbit interactions.

We investigate here the impact of an out-of-plane magnetic field and spin-orbit interaction on the spin conductivity of the two-dimensional Heisenberg model on a Lieb lattice. In this study, the Hamiltonian of the spin model has been transformed into a strongly interacting bosonic gas using a hard boson transformation. In this transformation, the occupation of a boson at each site is restricted by adding a hard core repulsion. To determine the excitation spectrum of the mapped model, the Green's function method has been employed. Based on the spectrum of the bosonic gas, the two-particle Green's function related to the spin conductivity of the two-dimensional Heisenberg model has been calculated. Computational results indicate that with an increase in the strength of the Dzyaloshinskii-Moriya interaction, the peak position in the dynamic spin conductivity shifts to higher frequencies under a constant magnetic field. However, the magnetic field does not affect the peak position of the dynamic spin conductivity. On the other hand, the intensity of dynamic spin conductivity increases with the strength of the Dzyaloshinskii-Moriya interaction. Our findings suggest that for a range of values of Dzyaloshinskii-Moriya interaction strength, the static transverse structure factor continuously decreases with the magnetic field. Additionally, for each value of the magnetic field, the temperature dependence of the static spin conductivity of localized electrons on the lattice exhibits a limited temperature peak.