Geometric Phase in Kitaev Quantum Spin Liquid

Quantum spin liquid has massive many-spin entanglement in the ground state; we can evaluate it by the entanglement entropy, but the latter cannot be observed directly by experiment. In this manuscript, we try to characterize its topological properties by the geometric phase. As we know, the usual adiabatic or non-adiabatic geometric phase cannot appear in the density matrix of entanglement entropy, so we extend it to the sub-geometric phase which can exist in the density matrix and have influence on the entanglement entropy, spin correlation function as well as other physical observable. We will demonstrate that the imaginary part of sub-geometric phase can deviate the resonance peak by an amount concerning with this phase and affect the energy level crossing, while the real part of sub-geometric phase may determine the stability of initial state, it may provide a complement on the selection rule of quantum transition.