Effects of the Spin-Orbit Coupling and the Superconductivity in simple-cubic alpha-Polonium

We have investigated the mechanism of stabilizing the simple-cubic (SC) structure in polonium (alpha- Po), based on the phonon dispersion calculations using the first-principles all-electron band method. We have demonstrated that the stable SC structure results from the suppression of the Peierls instability due to the strong spin-orbit coupling (SOC) in alpha-Po. Further, we have explored the possible superconductivity in alpha-Po, and predicted that it becomes a superconductor with Tc ~ 4 K. The transverse soft phonon mode at q ~ 2/3 R, which is greatly influenced by the SOC, plays an important role both in the structural stability and the superconductivity in alpha-Po. We have discussed effects of the SOC and the volume variation on the phonon dispersions and superconducting properties of alpha-Po.Comment: 5pages, 5figure

Pressure-induced Phonon Softenings and the Structural and Magnetic Transitions in CrO2_{2}

To investigate the pressure-induced structural transitions of chromium dioxide (CrO$_{2}$), phonon dispersions and total energy band structures are calculated as a function of pressure. The first structural transition has been confirmed at P$\approx$ 10 GPa from the ground state tetragonal CrO$_{2}$ (t-CrO$_{2}$) of rutile type to orthorhombic CrO$_{2}$ (o-CrO$_{2}$) of CaCl$_{2}$ type. The half-metallic property is found to be preserved in o-CrO$_{2}$. The softening of Raman-active B$_{1g}$ phonon mode, which is responsible for this structural transition, is demonstrated. The second structural transition is found to occur for P$\geq$ 61.1 GPa from ferromagnetic (FM) o-CrO$_{2}$ to nonmagnetic (NM) monoclinic CrO$_{2}$ (m-CrO$_{2}$) of MoO$_{2}$ type, which is related to the softening mode at {\bf q} = R(1/2,0,1/2). The third structural transition has been newly identified at P= 88.8 GPa from m-CrO$_{2}$ to cubic CrO$_{2}$ of CaF$_{2}$ type that is a FM insulator

Two Higgs doublet models for the LHC Higgs boson data at s=\sqrt{s}= 7 and 8 TeV

Updated LHC data on the new 126 GeV boson during the 7 and 8 TeV runnings strengthen the standard model Higgs boson interpretation further. Through the global $\chi^2$ analysis, we investigate whether the new particle could be one of the scalar particles in two Higgs doublet models. Four types (Type I, II, X and Y) are comprehensively studied. Taking the recent analysis on the spin-parity of the new boson, we consider two scenarios: the new boson is either the light CP-even one ($h^0$) or the heavy CP-even one ($H^0$). It is found that both scenarios are consistent with the new data, not only in the parameter regions near the decoupling limit but also in other regions far from the decoupling limit. In addition, the current data are compatible with the possibility that the light Higgs boson $h^0$ is hidden in the mass window of 90-100 GeV. The diphoton or $\tau\tau$ channel can provide a probe of this possibility by the enhanced signal rates.Comment: To appear in JHE