73 research outputs found
Estimation of the Doping Dependence of Antiferromagnetism in the Copper Oxide Material
Within the - model, we study the doping dependence of
antiferromagnetism in the copper oxide materials by considering quantum
fluctuations of spinons in the random-phase-approximation. The staggered
magnetization vanishes around doping for a reasonable parameter
value , which is in agreement with the experiments on copper oxide
materials.Comment: 14 page
Optical Conductivity in the Copper Oxide Materials
The frequency- and temperature-dependent optical conductivity of the copper
oxide materials in the underdoped and optimal doped regimes are studied within
the t-J model. The conductivity spectrum shows the unusual behavior at low
energies and anomalous midinfrared peak in the low temperatures. However, this
midinfrared peak is severely depressed with increasing temperatures, and
vanishes at higher temperatures.Comment: 11 pages, Revtex, Two figures are not included, and can be obtained
by reques
Pairing in graphene: A quantum Monte Carlo study
To address the issue of electron correlation driven superconductivity in
graphene, we perform a systematic quantum Monte Carlo study of the pairing
correlation in the t-U-V Hubbard model on a honeycomb lattice. For V=0 and
close to half filling, we find that pairing with d+id symmetry dominates
pairing with extended-s symmetry. However, as the system size or the on-site
Coulomb interaction increases, the long-range part of the d+id pairing
correlation decreases and tends to vanish in the thermodynamic limit. An
inclusion of nearest-neighbor interaction V, either repulsive or attractive,
has a small effect on the extended-s pairing correlation, but strongly
suppresses the d+id pairing correlation.Comment: 5 pages, 5 figure
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