Showing papers by "Somnath Ghosh published in 1982"

A spin-adapted linear response theory in a coupled-cluster framework for direct calculation of spin-allowed and spin-forbidden transition energies

Abstract: In this paper, we have spin-adapted our recently formulated linear response theory in a coupled-cluster framework. This allows us to calculate directly both the spin-allowed and the spin-forbidden transition energies from a single methodology. We have introduced rank-zero and rank-one spin operators to construct excitation operators for singlet-singlet and singlet-triplet transitions respectively and utilised the graphical methods of spin algebra to integrate the spin variables. It has been shown how a suitable parameterisation of the reduced Hugenholtz matrix elements of the excitation operator in terms of Goldstone matrix elements makes the resulting system of equations simple, compact and suitable for computer implementation. A pilot calculation has been performed to test the applicability of the theory.

Effect of size quantization on the effective mass in ultrathin films of n-Cd 3 As 2

Abstract: An attempt is made to investigate the effects of size quantization on the effective mass in ultrathin films ofn-Cd3As2. It is found that the effective mass at the Fermi level depends on the size quantum number due to the effect of crystal-field splitting, resulting in different effective masses at the Fermi level corresponding to different electric subbands. It is also observed that the different effective masses closely approach each other, for a given film thickness, with increasing electron concentration and, for a given electron concentration, with increasing film thickness.

Effect of Heavy Doping on the Electronic Heat Capacity in Semiconductors

Abstract: An attempt is made to derive an expression for the electronic heat capacity in heavily-doped semiconductors having Gaussian band-tails. With the help of this expression, the electronic heat capacity is studied as a function of the electron concentration corresponding to different temperatures, taking heavily-doped n-GaAs having Gaussian band-tails as an example. It is concluded that the nature of the dependence is determined exclusively by the movement of the Fermi level with changing electron concentration through the allowed energy states. Es wird der Versuch unternommen, einen Ausdruck fur die elektronische Warmekapazitat in stark-dotierten Halbleitern mit gausformigen Bandauslaufern abzuleiten. Mit Hilfe dieses Ausdrucks wird die elektronische Warmekapazitat als Funktion der Elektronenkonzentration entsprechend unterschiedlichen Temperaturen untersucht, wobei stark dotiertes n-leitendes GaAs mit gausformigen Bandauslaufern als Beispiel genommen wird. Es wird geschlossen, das die Art der Abhangigkeit ausschlieslich durch die Bewegung des Ferminiveaus mit der Anderung der Eletronenkonzentration durch die erlaubten Energiezustande bestimmt wird.