Person:

Rashba, Emmanuel

A theory of excitons in semiconductors in the Fractional Quantum Hall (FQH) Effect regime is presented. Non-conventional properties of magnetoexcitons in this regime originate from the fact that elementary excitations of the FQH phases carry fractional charges. Properties of excitons strongly depend on the separation h between electron and hole confinement planes. When this separation is not too small, h <EQ l, where l is the magnetic length, excitons look like quasiatoms consisting of a valence hole and several fractional charges. Charge fractionalization results in a multiple-branch structure of the exciton energy spectrum. Symmetric classification of the branches is proposed, and their relation to the low-energy part of the Hilbert space of the charged elementary excitations of the FQH phases is established. Spectroscopic implications of the spectra classification, including the selection rules, are discussed.

A theory of anyon excitons consisting of a valence hole and three quasielectrons with electric charges –e/3 is presented. A full symmetry classification of the k = 0 states is given, where k is the exciton momentum. The energy levels of these states are expressed by quadratures of confluent hypergeometric functions. It is shown that the angular momentum L of the exciton ground state depends on the distance between the electron and hole confinement planes and takes the values L = 3n, where n is an integer. With increasing k the electron density shows a spectacular splitting on bundles. At first a single anyon splits off of the two-anyon core, and finally all anyons become separated.

The connection between luminescence and different chapters of spectroscopy is discussed. Modern theoretical concepts and experimental techniques wiped away the boundaries that traditionally existed between them. Nevertheless, the basic notions of luminescence remain valid. Being focused on the dynamics and kinetics of electronically excited states, luminescence serves as an effective tool in solving numerous problems in contemporary solid-state physics. Electron–phonon interaction, excitons in disordered systems, the emission spectroscopy of the fractional quantum Hall effect and spin injection are discussed as specific examples.

In this Lecture, I display my personal perspective on the progress in physics of excitons during the last 50years. Preference is given to the areas of this extensive field which I participated. They include molecular excitons, giant oscillator strength inherent in bound excitons, self-trapping problem, strong magnetic fields including spectroscopy of the quantum Hall effect, etc. Critical importance of international scientific collaboration is also discussed.