31,006 research outputs found
Sign changes and resonance of intrinsic spin Hall effect in two-dimensional hole gas
The intrinsic spin Hall conductance shows rich sign changes by applying a
perpendicular magnetic field in a two-dimensional hole gas. Especially, a
notable sign changes can be achieved by adjusting the characteristic length of
the Rashba coupling and hole density at moderate magnetic fields. This sign
issue may be easily realized in experiments. The oscillations of the intrinsic
spin Hall conductance as a function of 1/ is nothing else but Shubnikov-de
Haas oscillations, and the additional beatings can be quantitatively related to
the value of the spin-orbit coupling parameter. The Zeeman splitting is too
small to introduce effective degeneracy between different Landau levels in a
two-dimensional hole gas, and the resonant intrinsic spin Hall conductance
appears in high hole density and strong magnetic field due to the transition
between mostly spin- holes and spin-3/2 holes is confirmed. Two likely
ways to establish intrinsic spin Hall effect in experiments and a possible
application are suggested.Comment: Accepted for publication in Applied Physics Letters, an enlarged
version, 5 pages, 4 fig
Superluminal Neutrinos in the Minimal Standard Model Extension
Most recently, the measurement of the neutrino velocity with the OPERA
detector in the CNGS beam shows unexpected indication, that the muon neutrino
velocity, , exceeds the velocity of light in the vacuum, , which is
obviously in contradiction with the most basic hypothesis of modern physics.
Within the framework of minimal Standard Model Extension, we discuss the
modified dispersion relation and consequently the velocity-energy relation of
muon neutrinos. The simplified models are fit to the OPERA data, Fermilab
experiment and MINO data. We find that minimal Standard Extension can describe
these long baseline superluminal neutrinos to a good accuracy. For the
well-known tension between the OPERA measurement and the Supernova 1987A
neutrino observation, we discussed two ways out of the contradiction.Comment: 7 pages, 2 figure
Spontaneous symmetry breakings in two-dimensional kagome lattice
We study spontaneous symmetry breakings for fermions (spinless and spinful)
on a two-dimensional kagome lattice with nearest-neighbor repulsive
interactions in weak coupling limit, and focus in particular on topological
Mott insulator instability. It is found that at -filling where
there is a quadratic band crossing at -point, in agreement with Ref. 1,
the instabilities are infinitesimal and topological phases are dynamically
generated. At -filling where there are two inequivalent Dirac
points, the instabilities are finite, and no topological phase is favored at
this filling without breaking the lattice translational symmetry. A
ferromagnetic quantum anomalous Hall state with infinitesimal instability is
further proposed at half-filling of the bottom flat band.Comment: 5 pages, 3 figures, Published in Phys. Rev.
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