Ballistic to hydrodynamic crossover in twisted bilayer graphene
ORAL
Abstract
At elevated temperatures, electron-electron (e-e) collisions dominate transport in high-mobility graphene, causing the flow of charge carriers to resemble that of classical fluids or gases and allowing for a hydrodynamic description [1][2]. However, experimental conditions are typically such that the onset of fluidity and truly hydrodynamic phenomena occur in a regime where electron-phonon scattering becomes significant. Twisted bilayer graphene (TBG), which has already seen success as a host for the study of strongly interacting electron systems [3], can provide an exceptional alternative platform to study hydrodynamic electron flow due to reduced Fermi velocity and thus a higher e-e scattering rate. Here we show that, at liquid helium temperatures, such devices exhibit micrometer-scale ballistic transport, probed using transverse magnetic focusing. At higher temperatures, we observe the development of a negative potential in the vicinity of the current injecting contact, which can be attributed to the onset of hydrodynamic electron behavior.
[1] D. Bandurin, et al. Science 351, 1055 (2016).
[2] D. Bandurin, et al. Nature Comm. 9, 4533 (2018).
[3] Y. Cao, et al. Nature 556, 43 (2018).
[1] D. Bandurin, et al. Science 351, 1055 (2016).
[2] D. Bandurin, et al. Nature Comm. 9, 4533 (2018).
[3] Y. Cao, et al. Nature 556, 43 (2018).
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Presenters
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Isabelle Phinney
- Massachusetts Institute of Technology