COMPETITION BETWEEN ANTIFERROMAGNETIC ORDER AND SPIN-LIQUID BEHAVIOR IN THE 2-DIMENSIONAL PERIODIC ANDERSON MODEL AT HALF FILLING

We study the two-dimensional periodic Anderson model at half filling using quantum Monte Carlo (QMC) techniques. The ground state undergoes a magnetic order-disorder transition as a function of the effective exchange coupling between the conduction and localized bands. Low-lying spin and charge excitations are determined using the maximum entropy method to analytically continue the QMC data. At finite temperature we find a competition between the Kondo effect and antiferromagnetic order which develops in the localized band through Ruderman-Kittel-Kasuya-Yosida interactions. © 1995 The American Physical Society.