You are cordially invited to the SCL online seminar of the Center for the Study of Complex Systems, which will be held on Thursday, 10 December 2020 at 14:00 on Zoom. The talk entitled

Construction of symmetry-adapted k.p Hamiltonians for semiconductor nanostructures

will be given by Milan Jocić (Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade). Abstract of the talk:

Since semiconductor materials are at the heart of almost all electronic devices, it is paramount to use the ones that have the best performances at the lowest cost. This is, in particular, important for solar cells, that convert clean solar energy to electricity. In recent years, metal-halide perovskites have drawn great attention in literature, since the power conversion efficiency of solar cells based on these materials has increased significantly and has reached more than 20% with the potential for improving even further. Understanding and modeling the electronic properties of these materials and their various nanostructures is of great importance.

Using ab initio methods like DFT for nanostructures is computationally very expensive, even with modern supercomputers. However, in this talk we will show that an accurate quantitative picture can be obtained with a k.p method by starting with Kohn-Sham (KS) states obtained from ab initio calculations for bulk structure. We will demonstrate this by comparing k.p with DFT calculations for the case of CdSe quantum wells [1]. We will obtain the analytical form and numerical parameters of well-studied 4x4 and 8x8 k.p Hamiltonians found in literature [2], for the case where spin-orbit coupling is omitted and included, respectively. Also, we will demonstrate an improvement over 4x4 and 8x8 Hamiltonians, by expanding the number of states from 4 (8) to 13 (26), which yields more accurate excited states. Another improvement can be made, by using the GW approximation within the many-body perturbation theory. This method can give more accurate bulk band gaps, which in turn yields improved results for nanostructures. At the end of the talk, we will present our latest results, for the inorganic halide-perovskite CsPbBr3 cubic quantum dot, and discuss further direction of our work.

[1] M. Jocić and N. Vukmirović, Phys. Rev. B 102, 085121 (2020).
[2] L. C. Lew Yan Voon and M. Willatzen, The k.p Method: Electronic Properties of Semiconductors (Springer-Verlag, Berlin, 2009).

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