Undercompensated kondo impurity with quantum critical point

Abstract

The low-temperature properties of a magnetic impurity of spin S interacting with an electron gas via anisotropic spin exchange are studied via Bethe's ansatz. For S>1/2 the impurity is only partially compensated at T = 0, leaving an effective spin that is neither integer nor half integer. The entropy has an essential singularity at H = T = 0, and the susceptibility and the specific heat follow power laws of H and T with nonuniversal exponents, which are the consequence of a quantum critical point. The results for the generalization to an arbitrary number of channels are also reported.