Letter abstract
Nature Physics 4, 627 - 630 (2008)
Published online: 20 July 2008 | doi:10.1038/nphys1022
Subject Categories: Electronics, photonics and device physics | Condensed-matter physics | Nanotechnology
Giant phonon-induced conductance in scanning tunnelling spectroscopy of gate-tunable graphene
Yuanbo Zhang1, Victor W. Brar1,2, Feng Wang1, Caglar Girit1,2, Yossi Yayon1, Melissa Panlasigui1, Alex Zettl1,2 & Michael F. Crommie1,2
The honeycomb lattice of graphene is a unique two-dimensional system where the quantum mechanics of electrons is equivalent to that of relativistic Dirac fermions1, 2. Novel nanometre-scale behaviour in this material, including electronic scattering3, 4, spin-based phenomena5 and collective excitations6, is predicted to be sensitive to charge-carrier density. To probe local, carrier-density-dependent properties in graphene, we have carried out atomically resolved scanning tunnelling spectroscopy measurements on mechanically cleaved graphene flake devices equipped with tunable back-gate electrodes. We observe an unexpected gap-like feature in the graphene tunnelling spectrum that remains pinned to the Fermi level (EF) regardless of graphene electron density. This gap is found to arise from a suppression of electronic tunnelling to graphene states near EF and a simultaneous giant enhancement of electronic tunnelling at higher energies due to a phonon-mediated inelastic channel. Phonons thus act as a 'floodgate' that controls the flow of tunnelling electrons in graphene. This work reveals important new tunnelling processes in gate-tunable graphitic layers.
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720, USA
Correspondence to: Yuanbo Zhang1 e-mail: zhyb@berkeley.edu
Correspondence to: Michael F. Crommie1,2 e-mail: crommie@berkeley.edu
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