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Condensed Matter Seminar: "Energy, momentum, and spin resolved tunneling of quantum Hall systems"

Event Type
Physics - Condensed Matter
190 ESB
Apr 5, 2019   1:00 pm  
Ray Ashoori, Massachusetts Institute of Technology
Originating Calendar
Physics - Condensed Matter Seminar

Transport measurements have revealed remarkable behaviors of the 2D electron system in a magnetic field, such as the quantum Hall effects and the existence of “edge-states” with quantized conductance. However, these and many other measurements have a main limitation in what they tell us about the system: they only have sensitivity to the behavior of electrons near the Fermi energy. Quantum mechanical tunneling, in contrast, can probe electronic states away from the Fermi level. This talk will introduce a contactless tunneling method that utilizes millions of short electrical pulses to induce tunneling currents into and out of 2D electronic systems and yields precise tunneling spectra of 2D system even in regimes where it is electrically insulating. The measurements have revealed remarkable new physics such as: (1) a sharp resonance in tunneling that arises from vibrations of 2D electrons in a “Wigner Crystal”; (2) structure appearing in tunneling spectra that give a direct measurement of the short-range interactions between electrons; (3) measurement and visualization of the 2D energy levels as a function of momentum; (4) observation of polarons and a novel phonon analog of the vacuum Rabi splitting; and (5) measurement of the unusual spin-polarization of the 2D electronic system in magnetic field.

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