R. G. Herb Condensed Matter Seminars

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Imaging the Breaking of Electrostatic Dams in Graphene for Ballistic and Viscous Fluids
Date: Thursday, December 1st
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Zachary Krebs , UW-Madison
Abstract: Under special conditions the charge carriers in a material can behave as a viscous fluid. In this work, we investigate such behavior by using scanning tunneling potentiometry to probe the nm-scale flow dynamics of electron fluids in graphene as they pass through constrictions defined by smooth and tunable in-plane p-n junction barriers. We observe that as the sample temperature and channel widths are increased, the electronic fluid flow undergoes a Knudsen-to-Gurzhi transition from ballistic to viscous flow that is characterized by a channel conductance that exceeds the ballistic limit, and suppressed charge accumulation against the barriers. Our results are well-modeled by finite-element simulations of 2D viscous current flow, and they illustrate how Fermi liquid flow evolves with carrier density, channel width, and temperature.
Host: Alex Levchenko
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