Quantum Monte Carlo simulation study of two-dimensional Hubbard model

The physical properties of strongly correlated fermionic systems, described by the two-dimensional Hubbard model with nearest neighbour hopping have b een studied using the path integral formulation along with quantum Monte Ca rlo simulation technique. The partition function of the fermionic system is evaluated within the usual path integral formulation treating beta, the in verse temperature as imaginary time and dividing it into small discrete int ervals. The singlet and triplet pairing correlation functions, nearest-neig hbour charge density correlations, local squared magnetic moment, double oc cupancy and total energy are studied as a function of interaction strength for various band fillings at different temperatures. This study leads to th e conclusions that the singlet pairing correlation decreases with increasin g interaction strength. The triplet pairing correlations for parallel spins show abrupt behaviour The extended singlet pairing correlation and triplet pairing correlations for anti-parallel spins show the slightly functuating behaviour at finite temperatures. The enhancement of local squared magneti c moment and decrement of double occupancy and increment of total energy wi th U at finite temperatures for half-filled, one-third-filled and one-fourt h-filled bands are also noted.