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Physics Colloquium: Classical E&M with a twist: A geometric Hall effect without magnetic field

February 12, 2020, 3:00 pm - 4:00 pm
Location Richardson Hall - 201
SponsorPhysics Club, Physics & AstronomyPosted InCollege of Science and Mathematics
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Classical E&M with a twist:  A geometric Hall effect without magnetic field

Dr. Nicholas Schade, Postdoctoral Scholar
James Frank Institute
University of Chicago

The classical Hall effect, the traditional means of determining charge-carrier sign and density in a conductor, requires a magnetic field to produce transverse voltages across a current-carrying wire.  In this talk, I will demonstrate a fundamentally novel use of geometry to create transverse potentials along curved paths without any magnetic field.  These potentials also reflect the charge-carrier sign and density, and they arise because a transverse electric field must accelerate the current radially in order to follow the curve.  I demonstrate this effect experimentally in curved graphene wires where the transverse voltages are as large as millivolts. The potentials are consistent with the doping and charge polarity as I switch the carrier sign.  In straight wires, I measure transverse voltage fluctuations with random polarity demonstrating that the current follows a complex, tortuous path.  This geometrically-induced potential offers a sensitive characterization of inhomogeneous current flow in thin films.