Quantized Berry phases of Kondo insulators

Abstract

Quantized Berry phases proposed as local order parameters for gapped quantum liquids at zero temperature are studied to detect the Kondo singlet phase which is known as a theoretical prototype of the Kondo insulators. We deal with the Kondo lattice model and the periodic Anderson model as two basic models for heavy fermions. We show that the Berry phase is actually quantized as trivial or non-trivial value, i.e., 0 or π, and analytically obtained both in the strong coupling limit of the Kondo lattice model and in the weak coupling limit of the periodic Anderson model. In addition, the Heisenberg Kondo lattice model is studied numerically by the quantized Berry phase.