Fermi surface topology and impurity-induced resonance state in BiS2_{2}-based superconductors

Within the two-orbital model for BiS$_{2}$-based superconductors, the effect from a single nonmagnetic impurity scattering on the superconducting-state is investigated in terms of the T-matrix approach. By considering three kinds of the typical Fermi surface topology which characterize the essential features of the doping dependence of the electronic structure in BiS$_{2}$-based superconductors, it is found that the impurity scattering on the superconducting-state with the conventional $s$-wave, the extended $s$-wave, the $\pm s$-wave, and the $d_{x^{2}-y^{2}}$-wave symmetries induces \textit{qualitatively} different resonance states due to the evolution of unique nodal structures on the Fermi surface with doping. These impurity-induced resonance states can be verified directly by the scanning tunneling microscopy experiments, and therefore they are proposed as a probe of the superconducting pairing symmetry in BiS$_{2}$-based superconductors.Comment: 5 pages, 7 figure

A proof of the strong no loop conjecture

The strong no loop conjecture states that a simple module of finite projective dimension over an artin algebra has no non-zero self-extension. The main result of this paper establishes this well known conjecture for finite dimensional algebras over an algebraically closed field.Comment: 9 page