Spectroscopy of Electron Liquids in Quantum Structures

Columbia University, New York NY

Investigators

Abstract

Technical This individual investigator award will support advanced optical spectroscopy studies of low-lying excitation modes of two-dimensional electron liquids in quantum Hall regimes. Collective excitations in the spin or charge degrees of freedom will be accessed by inelastic light scattering methods developed by the PI and collaborators. The primary interests are on the diverse and competing quantum phases of many particle systems that emerge at very low temperatures when electrons populate higher Landau levels in highly perfect systems. Being composed solely of electrons, the electron fluids and solids in the quantum Hall regimes are unique phases of matter that emerge at very low temperatures and high magnetic fields and that arise from the impact of fundamental Coulomb interactions among electrons. In these intriguing phases small changes in magnetic field may alter the statistics of quasiparticles from fermions to bosons and even to anyons. The goals of this body of research are the discovery and elucidation of the physics in these competing quantum phases of matter. The broader impacts stem from prospects of advancing the field by offering previously unavailable insights on striking quantum phases of matter. The group of the PI has strong representation of women and minorities, and significant links to leading scientists in the US and abroad. Non Technical When the spin, which is analogous to a small magnet attached to the electron, or electrical charge of electrons of systems containing many electrons existing in a certain state called the "quantum Hall regime" new electronic properties of the material containing them emerge. These properties will be measured using methods involving the reflection of light that were developed by the PI and his collaborators. The quantum Hall regimes occur at very low temperatures when electrons in nearly perfect man-made semiconductor structures are restricted to move on a flat plane with a magnetic field applied perpendicular to this plane. This group of electrons makes up a fluid or solid system of particles and is in a unique state of matter that emerges from the fact that each electron has a charge causing interactions to occur among them. In these intriguing electron systems under study, the collective motion of electrons is represented by what is known as ?quasiparticles? that may assume different characteristics that can be altered by applying small magnetic field changes to the system. The goal of the projected research is the discovery and elucidation of the physics that is at the origin of the competing electron states that emerge in these many electron systems. The research is of interest to an international community of scientists and to the general public that is amazed by manifestations of basic electron properties and their potential applications. The group of the PI offers significant opportunities to diverse groups of students and junior scientists to participate in world-class research.