18,819 research outputs found
Correlation-driven chiral superconductivity and chiral spin order in doped kagome lattice
We study the electronic instabilities of the Hubbard model in the 1/6
hole-doped Kagome lattice using the variational cluster approach. The 1/6 hole
doping is unique in the sense that the Fermi level is at the von Hove
singularity and the Fermi surface has a perfect nesting. In this case, a
density wave is usually realized. However, we demonstrate here that the chiral
superconducting state is most favorable when a small
Hubbard interaction U(U<3.0t) is introduced, and a scalar chiral spin order is
realized at large U(U>5.0t). Between them, a spin-disordered insulating state
is proposed.Comment: 5 pages, 4 figure
Quantum Phase Transition in Hall Conductivity on an Anisotropic Kagome Lattice
We study the quantum Hall effect(QHE) on the Kagom\'{e} lattice with
anisotropy in one of the hopping integrals. We find a new type of QHE
characterized by the quantization rules for Hall conductivity
and Landau Levels ( is an integer), which is different from any known type. This phase
evolves from the QHE phase with and in the isotropic case, which is realized in a system
with massless Dirac fermions (such as in graphene). The phase transition does
not occur simultaneously in all Hall plateaus as usual but in sequence from low
to high energies, with the increase of hopping anisotropy.Comment: 5 pages, 4 figure
Possible singlet and triplet superconductivity on honeycomb lattice
We study the possible superconducting pairing symmetry mediated by spin and
charge fluctuations on the honeycomb lattice using the extended Hubbard model
and the random-phase-approximation method. From to doping levels,
a spin-singlet -wave is shown to be the leading
superconducting pairing symmetry when only the on-site Coulomb interaction
is considered, with the gap function being a mixture of the nearest-neighbor
and next-nearest-neighbor pairings. When the offset of the energy level between
the two sublattices exceeds a critical value, the most favorable pairing is a
spin-triplet -wave which is mainly composed of the next-nearest-neighbor
pairing. We show that the next-nearest-neighbor Coulomb interaction is also
in favor of the spin-triplet -wave pairing.Comment: 6 pages, 4 figure
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