Band-edge properties of a semiconductor alloy: An NMR study of ${\mathrm{Hg}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Cd}}_{\mathit{x}}$Te

We report ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$ NMR measurements of narrow-gap ${\mathrm{Hg}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Cd}}_{\mathit{x}}$Te alloys in the range x=0.20–0.28. By studying temperature dependences, we have identified intrinsic Knight shifts in these alloys. This provides a measure of Hg orbital contributions to conduction-electron states, and we find a consistently strong average contribution from Hg s orbitals. Furthermore, we identify local variations in the Knight shift with spatial variations in conduction-electron densities and symmetries. These characteristics have been related to randomly populated sites within the alloys. We also discuss ${}_{}{}^{199}{}_{}{}^{}\mathrm{Hg}$ chemical shifts and their relation to local orbital charges.