Nonequilibrium properties of graphene probed by superconducting tunnel spectroscopy

Zihlmann, Simon and Makk, Peter and Castilla, Sebastian and Gramich, Joerg and Thodkar, Kishan and Caneva, Sabina and Wang, Ruizhi and Hofmann, Stephan and Schoenenberger, Christian. (2019) Nonequilibrium properties of graphene probed by superconducting tunnel spectroscopy. Physical Review B, 99 (7). 075419.

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Official URL: https://edoc.unibas.ch/73762/

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We report on nonequilibrium properties of graphene probed by superconducting tunnel spectroscopy. A hexagonal boron nitride (hBN) tunnel barrier in combination with a superconducting Pb contact is used to extract the local energy distribution function of the quasiparticles in graphene samples in different transport regimes. In the cases where the energy distribution function resembles a Fermi-Dirac distribution, the local electron temperature can directly be accessed. This allows us to study the cooling mechanisms of hot electrons in graphene. In the case of long samples (device length L much larger than the electron-phonon scattering length l(e-ph)), cooling through acoustic phonons is dominant. We find a crossover from the dirty limit with a power law T-3 at low temperature to the clean limit at higher temperatures with a power law T-4 and a deformation potential of 13.3 eV. For shorter samples, where L is smaller than l(e-ph) but larger than the electron-electron scattering length l(e-e), the well-known cooling through electron out-diffusion is found. Interestingly, we find strong indications of an enhanced Lorenz number in graphene. We also find evidence of a non-Fermi-Dirac distribution function, which is a result of noninteracting quasiparticles in very short samples.
Faculties and Departments:05 Faculty of Science > Departement Physik > Physik > Experimentalphysik Nanoelektronik (Schönenberger)
UniBasel Contributors:Schönenberger, Christian and Zihlmann, Simon and Makk, Peter and Gramich, Jörg Benedikt and Thodkar, Kishan
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Physical Society
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:16 Apr 2020 10:07
Deposited On:16 Apr 2020 10:07

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