Determinant Quantum Monte Carlo Study Of Doped Kondo Lattice

Heavy fermion materials are strongly correlated electron systems and often exhibit unconventional superconductivity. One of the central issues of highly debate is the nature of their various anomalous properties, which in recent years have brought more and more attention. In this thesis, we use the two-dimensional periodic Anderson model to simulate heavy fermion materials and apply determinant quantum Monte Carlo method (DQMC) to solve the model and study the process of hybridization and the effect of doping. Our main conclusions include:(1) A temperature-hybridization phase diagram in un-doped Kondo lattice. With increasing coupling between conduction electrons and localized f electrons, we find a metal-Kondo insulator phase transition at high temperatures and a metal-antiferromagnetic insulator-Kondo insulator transition at low temperatures. In the antiferromagnetic insulator regime, conduction electrons and f electron exhibit orbital-selective behavior.(2) In the antiferromagnetic (AFM) insulator regime and the Kondo insulator (KI) regime, when one f electron is removed, we find a spatial damping distribution in the hybridization strength due to interference effect. The spatial distribution of conduction electrons exhibits oscillation character in the AFM regime, while damping feature in the KI regime. The oscillation originates from hopping of conduction electrons, while impurity scattering is responsible for the damping behavior.(3) In the KI regime, impurity brings about bound states in the central hybridization gap of the spectral function. The weight of bound state is highest at the doped site of conduction electrons and decreases sequentially for the nearest neighbor site of f-electrons and c-electron and the next nearest neighbor f-electron site. When the impurity energy level is moved to the Fermi energy, these bound states move correspondingly toward the gap center.(4) Impurity’s interferences with the distribution of c-electrons, hybridization strength and bound states are restricted at nearest neighbor and next nearest neighbor sites.(5) In the KI regime, with more impurities doped into the lattice, the system undergoes a K1-metal phase transition. This transition is a1st order phase transition and the threshold is about30%. Thermodynamic properties change continuously across the transition, while transport properties change abruptly at the critical point due to percolation.