S K Joshi
Articles written in Pramana – Journal of Physics
Volume 1 Issue 5 November 1973 pp 212-229 Solids
Effect of interatomic electron correlation has been studied in narrow band solids using one-particle Green function method. We follow Hubbard in drawing an analogy with an alloy and find a self-consistent solution which predicts a finite lifetime for pseudoparticles. A specific case of a (non-magnetic) model system with half-filled parabolic band has been considered to calculate the pseudoparticle density of states function. Unlike the result in the presence of intra-atomic correlations alone, we find that this particular system is never an insulator, however large intra-atomic correlations may be.
Volume 11 Issue 6 December 1978 pp 673-695 Solids
Some of the cluster extensions of the coherent potential approximation (CPA) based on the effective medium theory have been critically studied with respect to the decoupling schemes involved in them. Their computational tractability has been examined and it has been found that the
Volume 12 Issue 3 March 1979 pp 269-274 Solids
Magnetic susceptibility of mixed-valence compounds has been calculated as a function of pressure using Falicov-Kimball model wherein the
Volume 14 Issue 3 March 1980 pp 191-199 Atomic And Molecular Physics
It has been shown that an analysis of radial stationary state wave functions of a particle in terms of their loops leads to such continuous, single-valued and finite functions which represent a practically convenient form of the radial wave packets of that particle at various positions. The radial wave packets have been used to investigate target distortion in electron-atom collisions. The distortion of the target is defined in terms of quantum-mechanical probabilities given by the wave packets. A closed expression which depends upon the position of the colliding electron, is obtained for the potential energy of the target in the field of the colliding electron.
Volume 14 Issue 5 May 1980 pp 321-326 Solid State Physics
Possibility has been explored of periodic time variation of intensity (quanturn beats) of radiation emitted from relativistic electrons channeling along the 〈110〉 axis of a crystal of f.c.c. (diamond) lattice structure.
Volume 15 Issue 2 August 1980 pp 175-179 Solid State Physics
Poor beam collimation leads to overcompensation of suppression of coherent bremsstrahlung in the axial channelling case. This fact has been used to study the effect of beam divergence on the radiation emitted by relativistic (axially) channelled positrons. It has been found that due to beam divergence in the experiment of Alguard and co-workers in which radiation of 56 MeV positrons channelling along 〈110〉 rows of a silicon crystal is observed, coherent bremsstrahlung becomes an important contributing factor to the high frequency part of the observed spectrum.
Volume 58 Issue 5-6 May 2002 pp 855-859 Superconductivity
Recently, angle-resolved photoemission spectroscopy measurements on Bi2Sr2CaCu2O8+δ, which possesses two CuO2 layers in the same unit cell, have yielded very interesting results. For the overdoped samples, these results show a splitting of electronic states near
Volume 58 Issue 5-6 May 2002 pp 861-866 Superconductivity
In the present work, we report the interplay of single particle and Cooper pair tunnelings on the superconducting state of layered high-
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