Милан Јоцић

07. децембра 2020.

У оквиру семинара Центра за изучавање комплексних система Института за физику у Београду, у четвртак, 10. децембра 2020. године у 14 часова путем Zoom платформе, Милан Јоцић (Лабораторија за примену рачунара у науци, Институт за физику у Београду) одржаће предавање:

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


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 4×4 and 8×8 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 4×4 and 8×8 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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Meeting ID: 847 8071 9484
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