Ellipsometric studies in the 1·5 to 5 eV range have been carried out on thin films of Cd_1−xMn_x Te and exhibitE₀,E₁ andE₁+Δ₁ transitions of the cubic semiconductors. The effect on these transitions upon irradiation by HeNe laser light, application of small alternating magnetic fields and the influence of both the fields, applied simultaneously, has been investigated. The observed critical point shifts have been interpreted on the basis of changes in the band structure of these thin films. This has been corroborated by theoretically calculating the effective number of electrons contributing to the transition per atom —N_eff.

Transport measurements were performed on over-doped samples of pristine and Pb-substituted Bi–Sr–Ca–Cu–O as a function of applied pressure up to 7 GPa. A monotonic decrease in the superconducting transition temperature accompanied by a change in the normal-state behaviour from metallic to semiconducting as a function of pressure is observed in the pristine sample. In the Pb-substituted sample, a monotonic decrease in the superconducting transition temperature up to ${\sim}$4.5 GPa followed by an increase after attaining a valley is observed. The pressure required to achieve this increase in T$_C$ in the Pb-substituted Bi–Sr–Ca–Cu–O was found to be much lower than that reported in the literature. High-pressure X-ray diffraction measurements performed on these samples reveal the absence of any structural phase transition. Furthermore, the values of the bulk moduli are found to increase in the Pb-substituted sample. The density functional theory calculations used to substantiate the obtained results indicate a pressure-induced buckling of the Cu–O plane in the Bi-2212 phase of the pristine sample. In the Pb-substituted sample, an increase in the number of electronic states available for conduction at the Fermi level and a pressure-dependent increase in the contribution of Pb towards the density of states are revealed from the calculations of the density functional theory.