Topological transitions in the site diluted Yao-Lee spin-orbital model*

The Yao-Lee (YL) model is an example of exactly solvable spin-orbital models that are generalizations of the original Kitaev model with extra local orbital degrees of freedom.

Similar to the Kitaev model, both spin and orbital degrees of freedom are effectively represented using sets of three-flavored Majorana fermions. The YL model exhibits a

 quantum spin liquid ground state with gapped and immobile Z2 fluxes and three-fold degenerate itinerant Majorana fermions. Our work demonstrated

that by introducing different time reversal symmetry (TRS) breaking fields one can split the degeneracy of Majorana fermions and close the gap for some of the bands, thus changing 

its topology. We calculated a comprehensive topological phase diagram for the YL model by considering various combinations of TRS breaking fields. This investigation revealed the

 emergence of distinct topological regions, each separated by nodal lines, signifying an evolution in the model's topological properties. We also investigated the impact of vacancies

 in the system. Our findings revealed that while vacancies modify the low-energy spectrum of the model, their presence has limited impact on the topological properties of the model, 

at least for small enough concentrations.