Highlighting non-parabolic bands in semiconductors

The parabolic approximation to the dispersion relation is a simplification that has often been adopted for the electronic band structure of most semiconductors near the edges of the fundamental bandgap. A non-parabolic approximation can be justified which will better describe the properties of semiconductors of narrow bandgaps for which a reduction to a quadratic form is not accurate enough, nor always warranted. It also stands for a better approximation in III–V compounds and for more complex thermoelectric materials. Some of the consequences of adopting non-parabolic bands will be highlighted, as well as approximate expressions for statistical properties. It is emphasized that many properties of semiconductors are not difficult to calculate with non-parabolic bands, which may have a wider range of applications in actual materials. These calculations can then be introduced in solid state physics and statistical physics courses through projects and homework problem sets. Specific examples are discussed designed to clarify basic physics concepts in semiconductors.

In memoriam. Orlando Zelaya-Angel’s contributions in Superficies y Vacío

Professor Orlando Zelaya Angel was an outstanding member of the research community on Solid State Physics. He served as President to the Sociedad Mexicana de Ciencia de Superficies y Vacío (SMCSyV; currently Sociedad Mexicana de Ciencia y Tecnología de Superficies y Materiales – SMCTSM), for the period 1995-1996. Professor Zelaya formed many researchers in Mexico, who continue developing research, either in Mexico, in their countries of origin, or abroad. Throughout the evolution of Superficies y Vacío, Professor Zelaya, contributed with sixteen articles on subjects ranging from thin films for optoelectronic applications, through hard coatings and studies on the process for production of Tortillas; covering most of his research areas of interest. Here is a subject-chronological compilation of the abstracts to his articles in Superficies y Vacío, after a year of his departure.

Response to Comment on “Investigation on Anomalous Thermal Quenching of Mn4+ Luminescence in A2XF6:Mn4+” [ECS J. Solid State Sci. Technol. 10 076007 (2021)]

Yan argued that an abnormal negative thermal quenching (TQ) of the A2XF6:Mn4+ fluoride phosphors was a pitfall caused by the diminishment in optical path lengths of the spectrofluorometer originating from the increasing volume of the phosphor (namely, thermal expansion) at elevated temperatures [S. Yan, J. Solid State Sci. Technol., 9, 106004 (2020)], but not from any intrinsic effects that can be rigidly modeled based on the solid state physics. We disagree with this comment and explain in more detail that abnormal negative TQ is surely explained by the intrinsic properties of the Mn4+-activated fluoride phosphors with denying his/her previous work.

PROPERTIES SYSTEMATIZATION FOR POLAR OXIDE CRYSTALS

The systematization of piezoelectic (PE), pyroelectric (PYE), electrooptic (EO), and nonlinear optical (NLO) properties has been carried out for the polar oxide crystals, used in functional electronics. The sharp extremal dependence has been found for the upper envelope of fuzzy sets for these properties taken in pairs. There is no any theoretical analysis of such dependencies in solid state physics up to now. It is shown nevertheless, that general view of such interrelationships is different in detail. The experimental points are near the upper envelope for the NLO-PE interrelationship, but there is still a lack of empirical data for EO-PE interrelationship. The highest acentric properties are observed in crystals of multicomponent oxide relaxors, partially studied only in the last 20 years.

Propagation of Wave Packets for Systems Presenting Codimension One Crossings

We analyze the propagation of wave packets through general Hamiltonian systems presenting codimension one eigenvalue crossings. The class of time-dependent Hamiltonians we consider is of general pseudodifferential form with subquadratic growth. It comprises Schrödinger operators with matrix-valued potential, as they occur in quantum molecular dynamics, but also covers matrix-valued models of solid state physics describing the motion of electrons in a crystal. We calculate precisely the non-adiabatic effects of the crossing in terms of a transition operator, whose action on coherent states can be spelled out explicitly.

In Memory of Alexander Sergeevich Ilyushin

Provides information about the deceased Alexander Sergeevich Ilyushin - Doctor of Physical and Mathematical Sciences, professor, Head of the Chair of Solid State Physics, Faculty of Physics, Lomonosov Moscow State University, Honored Professor of Lomonosov MSU, a full member of the Russian Academy of Natural Sciences, a well-known specialist in the field of structural solid state physics: basic biographical data, training at the Physics Faculty of Lomonosov MSU, postgraduate studies and work at the Solid State Physics Chair of Moscow State University, defense of candidate and doctoral dissertations, authorship of hundreds of scientific works, dozens of monographs and textbooks, pedagogical activity, leadership of the Solid State Physics Chair of MSU, membership in the academic councils of the Physics Faculty, participation and organization of Russian and international conferences, editorial scientific journals, creation and management of the Museum of History of the Physics Faculty of MSU, membership in the Russian Academy of Natural Sciences, management of its Division, creation and management of the Union of Philatelists of Russia, participation and organization of Russian and international philatelic exhibitions and conferences.