Solid-liquid transition and intermediate state formation in strongly correlated 2D systems

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Nontechnical abstractUnderstanding the ground states and phase transitions in two-dimensional(2D) electronic systems with strong electron-electron interactions has been a central unsettled problem in condensed matter physics. In addition to the strong correlations between 2D electrons, a further challenge in the problem is the unavoidable presence of disorder in real materials. Recent theoretical studies suggest that novel intermediate electronic phases might exist between the liquid and solid states in 2D systems when the interactions between particles are strong and the disorder is weak. However, it is far from clear whether such new intermediate states of matter exist in experiments. The goal of this project is to provide new insights to help unraveling this challenging problem in fundamental physics through new transport measurements on state-of-the-art samples with the highest purity. The results obtained through this research have broader implications to the deeper understanding of correlated condensed matter systems in general. Moreover, the project serves as a valuable platform to educate graduate and undergraduate students, and outreach pre-college students on cutting edge research in condensed matter and semiconductor physics. Student participants in the project receive hands on training in cryogenics, low temperature experimentation, signal and data analysis, and semiconductor processing and fabrication. These research experiences and skills are expected to prepare young students for continuing a successful career in either academia or industry. Technical abstractThe project aims to shed new light on the nature of strongly correlated two-dimensional (2D) carriers in semiconductor quantum structures through new electronic and thermoelectric transport experiments on state-of-the-art semiconductor gallium arsenide 2D heterostructures. The scope of this research mainly encompasses the study of the Coulomb interaction driven 2D Fermi liquid to Wigner solid phase transition in correlated 2D hole or electron systems. In the past, various many-body quantum liquid and solid phases of 2D electrons have been found in the presence of a strong magnetic field. However, very little is known in experiment about how the quantum 2D Wigner solid transforms into the liquid phase when the magnetic field is small or absent, despite much theoretical interests and investigations. In this project, complementary electronic and thermoelectric (entropic) transport techniques are employed to elucidate the 2D liquid-solid transition in strongly correlated 2D carrier systems with weak disorder, and explore the emergence of new intermediate phase(s) driven by Coulomb interaction effects, as predicted in a number of theoretical studies.