Optical and excitonic properties of transition metal oxide perovskites by the Bethe-Salpeter equation

We present a systematic investigation of the role and importance of excitonic effects on the optical propertiesof transitions metal oxide perovskites. A representative set of 14 compounds has been selected, including3d(SrTiO3, LaScO3,LaTiO3,LaVO3,LaCrO3,LaMnO3, LaFeO3, and SrMnO3), 4d(SrZrO3, SrTcO3,andCa2RuO4)and5d(SrHfO3,KTaO3, and NaOsO3) perovskites, covering a band gap ranging from 0.1 eVto 6.1 eV and exhibiting different electronic, structural, and magnetic properties. Optical conductivities andoptical transitions including electron-hole interactions are calculated through the solution of the Bethe-Salpeterequation (BSE) with quasiparticle energies evaluated by the single-shotG0W0approximation. The excitonbinding energies are computed by means of a model BSE, carefully benchmarked against the full-BSE method,in order to obtain well-converged results in terms ofk-point sampling. The predicted results are compared withavailable measured data, with an overall satisfactory agreement between theory and experiment

Single top or bottom production associated with a scalar in \gamma p collision as a probe of topcolor-assisted technicolor

In the framework of the topcolor-assisted technicolor (TC2) models, we study the productions of a single top or bottom quark associated with a scalar in \gamma-p collision, which proceed via the subprocesses c\gamma -> t\pi_t^0, c\gamma -> t h_t^0 and c\gamma -> b\pi^+_t mediated by the anomalous top or bottom coupling tc\pi_t^0, tch_t^0 and bc\pi_t^+. These productions, while extremely suppressed in the Standard Model, are found to be significantly enhanced in the large part of the TC2 parameter space, especially the production via c\gamma -> b\pi^+ can have a cross section of 100 fb, which may be accessible and allow for a test of the TC2 models.Comment: 13 pages, 4 figures, comments and references adde