Phase diagram for Hole-Doped Kitaev System on the Honeycomb Lattice

Abstract

In extended Kitaev models on the honeycomb lattice, off-diagonal interactions (e.g. the $\Gamma, \Gamma^{'}$ terms) give rise to non-Kitaev quantum spin liquid (QSL) and several magnetically ordered phases. In the present work, we dope holes to the system and study the resultant $t$-$K$-$\Gamma$-$\Gamma^{'}$ model by mean field theory. The interplay between the charge and spin degrees of freedom results in a rich phase diagram. Similar to doped cuprates, superconductors, pseudogap phases, fermi liquid, strange metal and paramagnetic phase are generated. What is different is that, more than one superconducting phases (including a topological one) and more than one pseudogap phases are obtained no matter what the original spin state is. The Chern number of the topological superconductor is either $\nu=\pm2$ or $\nu=\pm1$, depending on the ratio $\Gamma/ |K|$ in the spin channel. We further find that an intermediate in-plane magnetic field can slightly enlarge the size of the topological superconducting phase.