Physicists introduce a new mechanism for electronic optics in solid state systems

Electrons can interfere in the same way as water, sound waves, or light. When exploited in solid-state materials, such effects promise novel functionality for electronic devices, in which elements such as interferometers, lenses, or collimators could be integrated to control mirco and nanometer-scale electrons. So far, however, such effects have been demonstrated primarily in one-dimensional devices, for example in nanotubes, or under specific conditions in two-dimensional graphene devices. Writing in Physical Review X, a collaboration that includes Klaus Ensslin, Thomas Ihn, and Werner Wegscheider Physics Department groups at the Solid State Physics Laboratory and Oded Zilberberg at The Institute of Theoretical Physics, now presents a novel general scenario for performing electronic optics on two dimensions.

The main functional principle of optical interferometers is the interference of monochromatic waves that propagate in the same direction. In such interferometers, the interference can be observed as a periodic oscillation of the transmitted intensity as the wavelength of the light varies. However, the period of the interference pattern largely depends on the incident angle of the light, and as a result, the interference pattern is averaged if the light is sent through the interferometer at all possible angles at once. The same arguments apply to the interference of matter waves described by quantum mechanics, and in particular to interferometers where electrons interfere.

As part of his Ph.D. In the projects, experimentalist Matija Karalic and theorist Antonio Štrkalj have investigated the phenomenon of electronic interference in a solid-state system consisting of two coupled semiconductor layers, InAs and GaSb. They found that the band inversion and hybridization present in this system provide a novel transport mechanism that ensures interference that does not go away even when all angles of incidence occur. Using a combination of transport measurements and theoretical models, they discovered that their devices function like a Fabry-Pérot interferometer in which electrons and holes form hybrid states and interfere.

The importance of these results goes beyond the specific InAs / GaSb implementation explored in this work, since the reported mechanism requires only the two ingredients of band inversion and hybridization. Therefore, new paths are now being opened for the engineering of optical-electronic phenomena in a wide variety of materials.

Provided by the ETH Zurich Physics Department