Affordable Access

deepdyve-link deepdyve-link
Publisher Website

Signatures of evanescent transport in ballistic suspended graphene-superconductor junctions.

Authors
  • Kumaravadivel, Piranavan1
  • Du, Xu1
  • 1 Department of Physics and Astronomy, Stony Brook University, New York, USA.
Type
Published Article
Journal
Scientific Reports
Publisher
Springer Nature
Publication Date
Apr 15, 2016
Volume
6
Pages
24274–24274
Identifiers
DOI: 10.1038/srep24274
PMID: 27080733
Source
Medline
License
Unknown

Abstract

In Dirac materials, the low energy excitations behave like ultra-relativistic massless particles with linear energy dispersion. A particularly intriguing phenomenon arises with the intrinsic charge transport behavior at the Dirac point where the charge density approaches zero. In graphene, a 2-D Dirac fermion gas system, it was predicted that charge transport near the Dirac point is carried by evanescent modes, resulting in unconventional "pseudo-diffusive" charge transport even in the absence of disorder. In the past decade, experimental observation of this phenomenon remained challenging due to the presence of strong disorder in graphene devices which limits the accessibility of the low carrier density regime close enough to the Dirac point. Here we report transport measurements on ballistic suspended graphene-Niobium Josephson weak links that demonstrate a transition from ballistic to pseudo-diffusive like evanescent transport below a carrier density of ~10(10) cm(-2). Approaching the Dirac point, the sub-harmonic gap structures due to multiple Andreev reflections display a strong Fermi energy-dependence and become increasingly pronounced, while the normalized excess current through the superconductor-graphene interface decreases sharply. Our observations are in qualitative agreement with the long standing theoretical prediction for the emergence of evanescent transport mediated pseudo-diffusive transport in graphene.

Report this publication

Statistics

Seen <100 times