224 research outputs found
Fractional topological phase in one-dimensional flatbands with nontrivial topology
We show the existence of the fractional topological phase (FTP) in a
one-dimensional interacting fermion model using exact diagonalization, in which
the non-interacting part has flatbands with nontrivial topology. In the
presence of the nearest-neighbouring interaction , the FTP at filling
factor appears. It is characterized by the three-fold degeneracy and
the quantized total Berry phase of the ground-states. The FTP is destroyed by a
next-nearest-neighbouring interaction and the phase diagrams in the
plane is determined. We also present a physical picture of the
phase and discuss its existence in the nearly flatband. Within the picture, we
argue that the FTP at other filling factors can be generated by introducing
proper interactions. The present study contributes to a systematic
understanding of the FTPs and can be realized in cold-atom experiments.Comment: 5 pages, 5 figures. To appear in Phys. Rev.
Interaction effect in two-dimensional Dirac fermions
Based on the Dirac equations in the two-dimensional flux model, we
study the interaction effects both in nontrivial gapped and gapless Dirac
equations with numerical exact diagonalization method. In the presence of the
nearest and next nearest neighbor interactions: for nontrivial gapped Dirac
equation, the topological phase is robust and persists in a finite region of
the phase diagram; while for gapless Dirac equation, charge-density-wave and
stripe phases are identified and the phase diagram in plane is
obtained. When the next-next-nearest neighbor interaction is further included
to gapless Dirac equation, the topological phase expected in the mean-field
theory is absent. Our results are related to the possibility of dynamically
generating topological phase from the electronic correlations.Comment: 7 pages, 8 figures. More discussins are added; accepted for
publication in Physical Review
Interplay between single particle coherence and kinetic energy driven superconductivity in doped cuprates
Within the kinetic energy driven superconducting mechanism, the interplay
between the single particle coherence and superconducting instability in doped
cuprates is studied. The superconducting transition temperature increases with
increasing doping in the underdoped regime, and reaches a maximum in the
optimal doping, then decreases in the overdoped regime, however, the values of
this superconducting transition temperature in the whole superconducting range
are suppressed to low temperature due to the single particle coherence. Within
this superconducting mechanism, we calculate the dynamical spin structure
factor of cuprate superconductors, and reproduce all main features of inelastic
neutron scattering experiments in the superconducting-state.Comment: 7 pages, 3 figures, typo correcte
Cold-atoms on a two-dimensional square optical lattice with an alternating potential
The cold-atom on a two-dimensional square optical lattice is studied within
the hard-core boson Hubbard model with an alternating potential. In terms of
the quantum Monte Carlo method, it is shown explicitly that a supersolid phase
emerges due to the presence of the alternating potential. For the weak
alternating potential, the supersolid state appears for the whole range of
hard-core boson densities except the half-filling case, where the system is a
Mott insulator. However, for the strong alternating potential, besides the
supersolid and Mott insulating states, a charge density wave phase appears.Comment: 4 pages, 4 figure
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