University Calendar

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

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

Abstract:
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.