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Possible anisotropic spin-singlet pairings in Bi2X3 (X is Se or Te) are studied. Among six pairings compatible with the crystal symmetry, two novel pairings show nontrivial surface Andreev bound states, which form flat bands and could produce zero-bias conductance peak in measurements such as point-contact spectroscopy. By considering purely repulsive short-range Coulomb interaction as the pairing mechanism, the dominant super exchange terms are all antiferromagnetic, which would usually favor spin-singlet pairing in Bi2X3. Mean field analyses show that the interorbital pairing interaction favors a mixed spatial-parity anisotropic pairing state, and one pairing channel with zero-energy surface states has a sizable component. The results provide important information for future experiments. [ABSTRACT FROM AUTHOR]

We theoretically revisit graphene transport properties as a function of carrier density, taking into account possible correlations in the spatial distribution of the Coulomb impurity disorder in the environment. We find that the charged impurity correlations give rise to a density-dependent graphene conductivity, which agrees well qualitatively with the existing experimental data. We also find, quite unexpectedly, that the conductivity could increase with increasing impurity density if there is sufficient interimpurity correlation present in the system. In particular, the linearity (sublinearity) of graphene conductivity at lower (higher) gate voltage is naturally explained as arising solely from impurity correlation effects in the Coulomb disorder. [ABSTRACT FROM AUTHOR]

We have carried out calculations of the polarizabilities of the two-electron positive ions Li+, Be2+, B3+, C4+, N5+, and O6+ interacting with screened Coulomb potentials. Highly accurate correlated exponential wave functions are used to represent correlation effects on the charged particles. The dipole, quadrupole, and octupole polarizabilities for the screening parameters in the range 0-1a0-1 are reported. Reported results for the unscreened case are comparable with the available results and for the screened case show some interesting behavior with increasing nuclear charge. [ABSTRACT FROM AUTHOR]

We investigated the mixing and segregation of a system consisting of two different species of particles, having different charges, interacting through a pure Coulomb potential, and confined in a three-dimensional parabolic trap. The structure of the cluster and its normal mode spectrum are analyzed, as a function of the relative charge and the relative number of different types of particles. We found that (a) the system can be in a mixed or segregated state depending on the relative charge ratio parameter and (b) the segregation process is mediated by a first or second order structural phase transition which strongly influences the magic cluster properties of the system. [ABSTRACT FROM AUTHOR]