Evidence for local spots of viscous electron flow in graphene at moderate mobility

• Published in: arXiv.org
• Main Authors: Samaddar, Sayanti, Strasdas, Jeff, Janßen, Kevin, Just, Sven, Johnsen, Tjorven, Wang, Zhenxing, Burkay Uzlu, Li, Sha, Neumaier, Daniel, Liebmann, Marcus, Morgenstern, Markus
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 16.01.2022
• Subjects: Electric fields; Electrons; Field effect transistors; Flow mapping; Fluid dynamics; Fluid flow; Graphene; Physics - Disordered Systems and Neural Networks; Physics - Materials Science; Physics - Mesoscale and Nanoscale Physics; Physics - Other Condensed Matter; Room temperature; Scanning probe microscopy; Scattering; Semiconductor devices; Viscous flow
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2103.11466

Dominating electron-electron scattering enables viscous electron flow exhibiting hydrodynamic current density patterns such as Poiseuille profiles or vortices. The viscous regime has recently been observed in graphene by non-local transport experiments and mapping of the Poiseuille profile. Here, we probe the current-induced surface potential maps of graphene field effect transistors with moderate mobility using scanning probe microscopy at room temperature. We discover micron-sized large areas appearing close to charge neutrality that show current induced electric fields opposing the externally applied field. By estimating the local scattering lengths from the gate dependence of local in-plane electric fields, we find that electron-electron scattering dominates in these areas as expected for viscous flow. Moreover, we suppress the inverted fields by artificially decreasing the electron-disorder scattering length via mild ion bombardment. These results imply that viscous electron flow is omnipresent in graphene devices, even at moderate mobility.