Study of the Hubbard model on the triangular lattice using dynamical cluster approximation and dual fermion methods

摘要

We investigate the Hubbard model on the triangular lattice at half-fillingusing the dynamical cluster approximation (DCA) and dual fermion (DF) methodsin combination with continuous-time quantum Monte carlo (CT QMC) andsemiclassical approximation (SCA) methods. We study the one-particle propertiesand nearest-neighbor spin correlations using the DCA method. We calculate thespectral functions using the CT QMC and SCA methods. The spectral function inthe SCA and obtained by analytic continuation of the Pade approximation in CTQMC are in good agreement. We determine the metal-insulator transition (MIT)and the hysteresis associated with a first-order transition in the doubleoccupancy and nearest-neighbor spin correlation functions as a function oftemperature. As a further check, we employ the DF method and discuss theadvantages and limitation of the dynamical mean field theory (DMFT), DCA andrecently developed DF methods by comparing Green's functions. We find anenhancement of antiferromagnetic (AF) correlations and provide evidence formagnetically ordered phases by calculating the spin susceptibility.