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Amir Yacoby

4:00 p.m
November 5, 2008
Ford ITW Auditorium – Room 1-350



Amir Yacoby, Department of Physics, Harvard University
"Charge Fractionalization in Quantum Wires"
Abstract: Although the unit of charge in nature is a fundamental constant, the charge of individual quasiparticles in some low-dimensional systems may be fractionalized. Quantum one-dimensional (1D) systems, for instance, are theoretically predicted to carry charge in units smaller than the electron charge e. Unlike 2D systems, the charge of these excitations is not quantized and depends directly on the strength of the Coulomb interactions. For example, in a 1D system with momentum conservation, it is predicted that the charge of a unidirectional electron that is injected into the wire decomposes into right- and left-moving charge excitations carrying fractional charges f0*e and (1-f0)*e respectively. f0 approaches unity for non-interacting electrons and is less than one for repulsive interactions. Here, we provide the first experimental evidence for charge fractionalization in one dimension. Unidirectional electrons are injected at the bulk of a wire and the imbalance in the currents detected at two drains on opposite sides of the injection region is used to determine f0. Our results elucidate further the collective nature of electrons in one dimension. [1]

[1] H. Steinberg, A. Yacoby, et al., Nature Physics 4, 116 (2008), "Charge fractionalization in quantum wires"

Bio: Professor Yacoby is an experimental condensed matter physicist at Harvard University in the Department of Physics. He received his PhD from the Weizmann Institute of Science in 1994, and researched at Bell Labs in Murray Hill before joining the faculty at the Weizmann Institute where he remained until 2006. His current research interests are focused at unraveling the underlying phenomena governing low dimensional systems. Starting with two dimensional electron systems, the group uses novel scan probe techniques that are capable of detecting electric charge with a resolution of 10-4 of one electron and spatial resolution of 100 nm. This technique enables them to image the distribution of electrons and the way they localize in space in various material systems such as GaAs or single monolayers of graphite as well as under various ground state conditions such as the integer and fractional quantum Hall effect. Of particular interest is the 5/2 fractional quantum Hall ground state where the elementary excitations carry a fractional charge of e/4 and obey non-Abelian statistics. Such a system is a model system for topological quantum computation. Reducing dimensionality further to one dimension opens up a fascinating world where electrical conduction is strongly governed by the interaction between electrons. Here the group explores experimentally Luttinger liquid behavior whose strongest manifestation is the separation of spin and charge of the elementary excitations. Finally going down to zero dimensional systems, know as quantum dots, the group studies various approaches to storing and manipulating quantum information using the spin of individual electrons. Most recently, a new approach for nanoscale magnetic field sensing has been developed using a single electron spin in diamond.

Hosted by Matthew Grayson
Northwestern University Robert R. McCormick School of Engineering and Applied Science Electrical Engineering and Computer Science Department