Pseudospin Degree of Freedom in Strongly Correlated Electronic Systems

The purpose of this work is to observe ferromagnetic phase transitions near filling factors 2 and 3 in an 2DES with an AlAs quantum well, as well as to characterize the observed features in terms of spin and pseudospin polarization using electron spin resonance spectroscopy. For a continuous and controlled change in the valley polarization, it is necessary to implement a technique for applying in-plane strain to the 2DES under low temperature conditions. In contrast to the transport measurements, with which AlAs quantum wells have been widely studied, the ESR spectroscopy has several significant advantages. It makes it possible to directly detect the value of the spin and pseudospin polarization of the system, to distinguish between spin and pseudospin transitions accompanied by similar features in the longitudinal resistance, and is also applicable at lower temperatures, when the feature in the longitudinal resistance may completely disappear. In the future, the possibility of using the electron spin resonance spectroscopy and continuous application of deformation to the 2DES will make it possible to experimentally study the finest effects that arise in strongly correlated systems, such as fractional states of the quantum Hall effect, composite fermions, valley skyrmions, and to study the spin-valley interaction.