In the article published in Nanotechnology, researchers from Shri Govindram Seksaria (SGS) Institute of Technology and Science, Indore, India have theoretically analysed the effect of strain and magnetic fields on the spectral characteristics and coherent optical response of a single self-assembled semiconductor QD. The QD material that was considered is CdSe grown on a ZnSe wetting layer, which is gaining importance due to the wide bandgap and deep confinement potential offered by this combination. Luttinger Hamiltonian formalism was used to account for the complex valence-band structure consisting of light and heavy holes. The energy levels and the wavefunctions were obtained by numerical diagonalization of the Hamiltonian. The absorption spectra are analyzed using these energy eigenvalues and eigenfunctions. The transient optical response was calculated following the effective semiconductor Bloch equation approach.

The researchers observed that the strain effects incorporated in terms of deformation potential lead to a substantial blue shift of the energy levels and also cause a relative shift of heavy and light hole energy levels. Multiple oscillations arising due to quantum interference are seen in the temporal characteristics of the induced polarization; the frequency of these oscillations can be enhanced by increasing the magnetic field.

Understanding coherent oscillations in semiconductor nanostructures is an extremely useful technique to achieve coherent optical control of excited states and minimizing decoherence, which forms the basis for quantum computation.