We discuss the surface spectral function of superconductors realized from a topological insulator, such as the copper-intercalated Bi2Se3. These functions are calculated by projecting bulk states to the surface for two different models proposed previously for the topological insulator. Dependence of the surface spectra on the symmetry of the bulk pairing order parameter is discussed with particular emphasis on the odd-parity pairing. Exotic spectra like an Andreev bound state connected to the topological surface states are presented.

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To resolve the discrepancies of the superconducting order parameter in quasi-two-dimensional NbSe 2 , comprehensive specific-heat measurements have been carried out. By analyzing both the zero-field and mixed-state data with magnetic fields perpendicular ͑H Ќ c͒ to and parallel ͑H ʈ c͒ to the c axis of the crystal and using the two-gap model, we conclude that ͑1͒ more than one energy scale of the order parameter is required for superconducting NbSe 2 due to the thermodynamic consistency; ͑2͒ ⌬ L = 1.26 meV and ⌬ S = 0.73 meV are obtained; ͑3͒ N S ͑0͒ / N͑0͒ = 11% -20%; ͑4͒ the observation of the kink in ␥͑H͒ curve suggests that the two-gap scenario is more favorable than the anisotropic s-wave model to describe the gap structure of NbSe 2 ; and ͑5͒ ⌬ S is more isotropic and has a three-dimensional-like feature and is located either on the Se or the bonding Nb Fermi sheets.

We calculate thermopower of clean and impure bilayer graphene systems. Opening a band gap through the application of an external electric field is shown to greatly enhance the thermopower of bilayer graphene, which is more than four times that of the monolayer graphene and gapless bilayer graphene at room temperature. The effect of scattering by dilute charged impurities is discussed in terms of the self-consistent Born approximation. Temperature dependence of the thermopower is also analyzed.Comment: 8 pages, 5 figures; An inconsistency in the definitions of Eq.(17) and (18) in version 1 is found and correcte