Phys. Rev. B 84, 073405 (2011) [6 pages]

Coulomb gap in graphene nanoribbons

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S. Dröscher1, H. Knowles1, Y. Meir2, K. Ensslin1, and T. Ihn1
1Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
2Physics Department, Ben Gurion University, Beer Sheva IL-84105, Israel

Received 14 June 2011; published 19 August 2011

We investigate the density- and temperature-dependent conductance of graphene nanoribbons with varying aspect ratio. Transport is dominated by a chain of quantum dots forming spontaneously due to disorder. Depending on ribbon length, electron density, and temperature, single or multiple quantum dots dominate the conductance. Between conductance resonances, cotunneling transport at the lowest temperatures turns into activated transport at higher temperatures. The density-dependent activation energy resembles the Coulomb gap in a quantitative manner. Individual resonances show signatures of multilevel transport in some regimes, and stochastic Coulomb blockade in others.

©2011 American Physical Society

73.23.-b, 72.80.Vp