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/$B$ 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-$-{1/2}$ 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, $v_{\nu}$, exceeds the velocity of light in the vacuum, $c$, 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 $\frac{1}{3}$-filling where there is a quadratic band crossing at $\Gamma$-point, in agreement with Ref. 1, the instabilities are infinitesimal and topological phases are dynamically generated. At $\frac{2}{3}$-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.