Spin excitations in Kondo insulator YbB12

Cluster based analysis show that the observable three-level YbB12YbB12 spin excitations character can be reproduced in the framework of the asymmetric variant of periodic Anderson model with a singlet ground state and two electrons per site. For the macroscopic system the effective Hamiltonian with the direct f–ff–f exchange is justified and the dynamic spin susceptibility of f-electrons is found. It is shown that the lowest spin excitation dispersion has minimum at the antiferromagnetic vector as observed in the experiment. The distinctive feature of analysis is the using of singlet and triplet basis operators.