Quantum Monte Carlo simulation on Hubbard model for high temperature superconductivity

Miscellaneous · Wed Jan 01 00:00:00 EST 1992

OSTI ID:6271162

Bhattacharya, A

An extended Hubbard model on a copper-oxygen lattice in two dimension has gained considerable attention in the context of high temperature superconductivity. In this dissertation various properties of this model Hamiltonian have been explored using both the finite temperature path integral Monte Carlo and the Gutzwiller Variational Monte Carlo methods. Antiferromagnetism appears to occur at half-filling when oxygen-p level and copper-d level have substantial different energies. The dependence of the variational parameters on the Hamiltonian parameters are discussed. It is also shown that a simplified model keeping only the Coulomb correlation on the copper sites retains antiferromagnetism at half-filling with correct local moment and distribution of holes on copper and oxygen sites. The simulations for a small cluster indicate the possibility of extended s-wave and d-wave pairing in the extended Hubbard model. Motivated by the earlier work on flux-phases as possible ground states for the t-J model, which can be derived as a large-U limit of a single band Hubbard model, these flux phase states are studied for a single band Hubbard model using Gutzwiller's variational ansatz. Contrary to the previous results for the t-J model, the ground state of the Hubbard model is found to be always paramagnetic or antiferromagnetic. Near half-filling the t-J model with no double occupancy is dominated by magnetic energy, while Hubbard model with partial double occupancy is dominated by kinetic energy. When flux-phases are introduced into the Hubbard model, the decrease in magnetic energy is not enough to compensate the cost of kinetic energy increment.

• Research Organization: Maryland Univ., College Park, MD (United States)
• OSTI ID: 6271162
• Resource Relation: Other Information: Ph.D. Thesis
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
HIGH-TC SUPERCONDUCTORS
HUBBARD MODEL
COMPUTERIZED SIMULATION
MONTE CARLO METHOD
ANTIFERROMAGNETISM
COPPER
GROUND STATES
OXYGEN
CALCULATION METHODS
CRYSTAL MODELS
ELEMENTS
ENERGY LEVELS
MAGNETISM
MATHEMATICAL MODELS
METALS
NONMETALS
SIMULATION
SUPERCONDUCTORS
TRANSITION ELEMENTS
360207* - Ceramics
Cermets
& Refractories- Superconducting Properties- (1992-)