12:00 pm GCIS W301/W303
What is the Ultimate Conductance of Hydrodynamic Electrons?
Electrical resistance usually originates from lattice imperfections.However, even a perfect lattice has a fundamental resistance limit, given bythe Landauer conductance of its discrete modes. This resistance, shown by Sharvinto appear at the contacts to electronic devices, sets the ultimate conduction limitof non-interacting electrons. Recent years have seen growing evidence ofhydrodynamic electronic phenomena, prompting recent theories to ask whether liquidelectrons can radically break this fundamental Landauer-Sharvin limit. In thistalk I will present imaging experiments of electronic flows in high-mobilitygraphene Corbino devices to answer this question. First, by imaging ballisticflows at low temperatures, we observe a Landauer-Sharvin resistance that doesnot appear at contacts but is instead distributed throughout the bulk. This underpinsthe phase-space origin of this resistance - as emerging from spatial gradients inthe number of conduction modes. At elevated temperatures, we identify andaccount for the contribution of electron-phonon scattering and reveal the purehydrodynamic flow. Strikingly, we find that hydrodynamic electron flow eliminatescompletely the bulk Landauer-Sharvin resistance. Finally, by adding smallmagnetic fields, we image swirling magneto-hydrodynamic flows, revealing the keyemergent length-scale predicted by hydrodynamic theories – the Gurzhi length.These observations demonstrate that electronic fluids can dramatically overcomethe limitations of ballistic electrons, with important implications for fundamentalscience and future technologies.