Osipyan Institute of Solid State Physics Russian Academy of Sciences (ISSP RAS), Chernogolovka, Russia.

报告人简介

Anton Shchepetilnikov is a senior researcher at the Osipyan Institute of Solid State Physics, Chernogolovka. He received a B.S. from the Moscow Institute of Physics and Technology, Mocow in 2010, and an M.S. from the Moscow Institute of Physics and Technology, Mocow in 2012. He received his Ph.D. in Physics from the Ossipyan Institute of Solid State Physics, Chernogolovka working with prof. Igor Kukushkin in 2016. In his thesis work he focused on the spin properties of GaAs/AlGaAs heterostructures probed by electron spin resonance. After completing his Ph.D, Anton accepted a position at the Laboratory of Nonequilibrium Electron Processes, where he has been since that time. His research interests span both transport and spin properties of low dimensional semiconductor systems at sub-Kelvin temperatures. Much of his work has been devoted to the applied research in the field of sub-THz imaging and detector development.

报告摘要

At low temperatures, the strongly-correlated two-dimensional electron systems possess a rich physics with a set of unconventional ground states and a non-trivial spectrum of various charge and spin excitations. Although most of the theoretical ideas in the field were put forward almost a century ago, some of these concepts have been experimentally realized only recently leaving much room for further investigations. Here we discuss the experimental study of strongly-correlated electron systems with the aid of a microwave and sub-THz spectroscopy. This method provides an in-depth insight into the physics of strongly-correlated electron systems, as the energy of various excitations in the electron spectrum falls within this frequency range. We combine measurements of transport characteristic of the 2D channel with excitation by the microwave and sub-THz radiation, so that the electron system itself serves as a sensitive bolometric detector of the radiation absorption. For example, this approach proved itself extremely useful for the detection of spin resonances.

The talk focuses on the spectroscopic studies of ZnO/MgZnO and GaN/AlGaN heterojunctions, as well as AlAs/AlGaAs quantum wells. These structures boast off relatively large effective mass ensuring the increased energy of e-e interactions compared to their characteristic kinetic energy, favoring the crucial role of many-particle correlations. The first part of the talk is devoted to the electron spin resonance experiments. Through the use of spin resonance, we have examined a series of ferromagnetic phase transitions brought about by the strong e-e interactions at different filling factors of the quantum Hall effect in tilted magnetic fields. These transitions are accompanied by a macroscopic change in either spin or pseudospin polarization. Furthermore, we were able to observe the modification of electron spin splittings caused by the entanglement of the spin degree of freedom and the in-plane motion of electrons due to the spin-orbit interaction. Analyzing these splittings enabled us to extract the spin-orbit parameters in all of the studied material systems. The last part of the presentation focuses on the studies of the microwave induced resistance oscillations under the conditions of strong e-e interactions. We demonstrate that in contrast to a common belief the period of these oscillations deviates from the predicted single particle value and is strongly influenced by e-e correlations.

报告地点： M楼255会议室

邀请人：李永庆   研究员

联系人：孙丽（18601300418）

主办单位： 应用物理中心