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Monday, November 17, 2014 at 4:00pm to 5:00pm
Rockefeller Hall, Schwartz Auditorium
Central Campus
Physics Colloquium, Dr. Raymond Ashoori, MIT. Refreshments at 3:30 pm
Title: A New Method for Electron Tunneling Spectroscopy of Semiconductors, Insulatorss, and Graphene
Host: Paul McEuen
Abstract: Tunneling spectroscopy has a powerful track record in condensed matter physics. For instance, tunneling measurements were critical to validating the BCS theory of superconductivity. In low-dimensional electronic systems, tunneling measurements are often stymied by low sample conductivity, gating effects, heating due to the tunneling current, and unknown voltage drops. This talk presents a pulsed method for studying tunneling, “time domain capacitance spectroscopy” (TDCS), that eliminates these problems and even allows precise determination of tunneling spectra of localized states in insulators. Moreover, the energy resolution of the technique is limited only by the sample temperature. In semiconducting 2D systems this pulsed tunneling method directly reveals quasiparticle lifetimes, exchange splittings, and several striking and unexpected features. The talk will also describe the observation in graphene of the long sought “Hofstadter Butterfly” and work to apply TDCS to graphene and other atomically thin layered systems.
Sue Sullivan
607/255-7562
Dr. Raymond Ashoori
MIT