• S Srinivasan

      Articles written in Pramana – Journal of Physics

    • Surface exciton modes for plane and spherical semiconductor-metal interfaces

      S Srinivasan Sudhanshu S Jha

      More Details Abstract Fulltext PDF

      An approximate method is developed for investigating the nature of interface exciton modes in a composite spatially dispersive medium. The method is general enough to be applicable to any composite system, in which each component is described by an arbitrary bulk dielectric functionε(q, ω). It is based on the extension of the usual electrostatic-image method of solving the Poisson’s equation, in the presence of an external point charge in the system. We have applied our general method to a composite system of a finite metal slab surrounded by a semiconductor on one side and the vacuum on the other side. Similarly, we have also considered the case of a metallic sphere of radiusR, surrounded by a semiconductor, with a spherical interface between them. With assumed spatially dispersive model dielectric functions for the bulk metal and the bulk semiconductor, the nature of the electron-electron interaction and the interface exciton modes in the metallic region are obtained in both the cases. For the relevant size of the metal large compared to the atomic dimensions over which the bulk dielectric functions are non-local due to the spatial dispersion, it is shown that one can obtain the interface exciton modes by first defining new effective dielectric functions for each of the media making the particular interface, and then using the usual expression which determines the modes in the non-dispersive case.

    • Superconducting transition temperature for semimetals like bismuth

      S Srinivasan P Bhattacharyya Sudhanshu S Jha

      More Details Abstract Fulltext PDF

      The superconducting transition temperatureTc for semimetals like bismuth has been calculated as a function of the densitync of the electron and hole charge carriers. A simplified two-band model for describing the longitudinal dielectric function for such a system has been used in our model calculation. We find that the attractive interaction responsible for the instability of the normal ground state comes not only from the exchange of lattice phonons, but also from the electronhole sound mode, provided the ratio of the averaged hole to electron mass,mh/me ≠ 1. We have compared our theoretical values ofTc(nc) with experimental results for bismuth under hydrostatic pressure, and find reasonable agreement ifmh/me is assumed to have a value which is only slightly larger than that at atmospheric pressures. A linear variation of the negative band gap as a function of pressure has been assumed for the sake of this comparison.

    • Lattice static properties of vacancy clusters and interstitials in hcp magnesium: Computer simulation studies

      H K Sahu S Srinivasan K Krishan

      More Details Abstract Fulltext PDF

      Computer simulation studies have been made to investigate the static properties of mono-, di- and tri-vacancy clusters and of self-interstitials in hcp magnesium in different configurations. Three interatomic potentials have been chosen for which the results have been compared. A crystallite containing about 1500 atoms and a model with the interatomic interaction extending upto the fourth neighbour distance have been used. Relaxation field, defect relaxation and formation energies, strength dipole tensors and relative changes in volume in the above defects have been computed and our final results compared with those of earlier workers. The formation energies of the defects are highly sensitive to the choice of the potential whose detailed structure guides the nature of relaxation and the dipole tensors. Calculations have been done for octahedral, tetrahedral and dumb-bell interstitials of which the last is found to be the most stable.

  • Pramana – Journal of Physics | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2021-2022 Indian Academy of Sciences, Bengaluru.