Field-induced phase transitions in a Kondo insulator

We study the magnetic-field effect on a Kondo insulator by exploiting the periodic Anderson model with the Zeeman term. The analysis using dynamical mean field theory combined with quantum Monte Carlo simulations determines the detailed phase diagram at finite temperatures. At low temperatures, the magnetic field drives the Kondo insulator to a transverse antiferromagnetic phase, which further enters a polarized metallic phase at higher fields. The antiferromagnetic transition temperature T-c takes a maximum when the Zeeman energy is nearly equal to the quasiparticle gap. In the paramagnetic phase above T-c, we find that the electron mass gets largest around the field where the quasiparticle gap is closed. It is also shown that the induced moment of conduction electrons changes its direction from antiparallel to parallel to the field.