Lateral optical anisotropy of type-II interfaces in the tight-binding approach

We have developed the tight-binding theory to study electronic and optical properties of type-II heterostructures CA/C'A' grown from the zinc-blende semiconductors CA and C'A' along the crystallographic direction [001]. The sp^3s* nearest-neighbor tight-binding model with allowance for the spin-orbit interaction is used to calculate the energy states and the in-plane linear polarization of the spatially-indirect band-edge photoluminescence of InAs/AlSb and ZnSe/BeTe multi-layered structures. The interface parameters for a pair of the nonstandard planes C-A' or C'-A are considered as fitting variables. A wide range of these parameters are shown to allow Tamm-like hole states localized at the interfaces. The theory leads to giant values of the light polarization in the both type-II heterosystems in agreement with existing experimental findings.Comment: 9 pages, 6 figures, submitted to Phys. Rev.

Tight-binding description of inorganic lead halide perovskites in cubic phase

Band structure of inorganic lead halide perovskites is substantially different from the band structure of group IV, III-V and II-VI semiconductors. However, the standard empirical tight-binding model with sp3d5s* basis gives nearly perfect fit of band structure calculated in the density functional theory. The tight-binding calculations of ultrathin CsPbI3 layer show good agreement with the corresponding DFT calculations. The parameters corrected for the experimental data allow for the numerically cheap atomistic calculations of inorganic perovskite nanostructures.Comment: 6 pages, 4 figure

Spin and valley-orbit splittings in SiGe/Si heterostructures

Spin and valley-orbit splittings are calculated in SiGe/Si/SiGe quantum wells (QWs) by using the tight-binding approach. In accordance with the symmetry considerations an existence of spin splitting of electronic states in perfect QWs with an odd number of Si atomic planes is microscopically demonstrated. The spin splitting oscillates with QW width and these oscillations related to the inter-valley reflection of an electron wave from the interfaces. It is shown that the splittings under study can efficiently be described by an extended envelope-function approach taking into account the spin- and valley-dependent interface mixing. The obtained results provide a theoretical base to the experimentally observed electron spin relaxation times in SiGe/Si/SiGe QWs.Comment: 10 pages, 5 figure

Untangling the valley structure of states for intravalley exchange anisotropy in lead chalcogenides quantum dots

We put forward a generalized procedure which allows to restore the bulk-like electron and hole wave functions localized in certain valleys from the wave functions of quantum confined electron/hole states obtained in atomistic calculations of nanostructures. As a demonstration, the procedure is applied to the lead chalcogenide quantum dots to extract the effective intravalley Hamiltonian of the exchange interaction for the ground exciton state PbS and PbSe quantum dots. Renormalization of the anisotropic intravalley matrix elemets of velocity is also calculated. The results demonstrate that the matrix elements of intravalley exchange in PbS quantum dots are much more anisotropic than ones in PbSe.Comment: 11 pages, 7 figures, 1 tabl