4,807 research outputs found
Mott Insulator-Superfluid Transition in a Generalized Bose-Hubbard Model with Topologically Non-trivial Flat-Band
In this paper, we studied a generalized Bose-Hubbard model on a checkerboard
lattice with topologically nontrivial flat-band. We used mean-field method to
decouple the model Hamiltonian and obtained phase diagram by Landau theory of
second-order phase transition. We further calculate the energy gap and the
dispersion of quasi-particle or quasi-hole in Mott insulator state and found
that in strong interaction limit the quasi-particles or the quasi-holes also
have flat bands.Comment: 13 figures, 9 page
3D quantum Hall effect of Fermi arcs in topological semimetals
The quantum Hall effect is usually observed in 2D systems. We show that the
Fermi arcs can give rise to a distinctive 3D quantum Hall effect in topological
semimetals. Because of the topological constraint, the Fermi arc at a single
surface has an open Fermi surface, which cannot host the quantum Hall effect.
Via a "wormhole" tunneling assisted by the Weyl nodes, the Fermi arcs at
opposite surfaces can form a complete Fermi loop and support the quantum Hall
effect. The edge states of the Fermi arcs show a unique 3D distribution, giving
an example of (d-2)-dimensional boundary states. This is distinctly different
from the surface-state quantum Hall effect from a single surface of topological
insulator. As the Fermi energy sweeps through the Weyl nodes, the sheet Hall
conductivity evolves from the 1/B dependence to quantized plateaus at the Weyl
nodes. This behavior can be realized by tuning gate voltages in a slab of
topological semimetal, such as the TaAs family, CdAs, or NaBi. This
work will be instructive not only for searching transport signatures of the
Fermi arcs but also for exploring novel electron gases in other topological
phases of matter.Comment: 5 pages, 3 figure
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