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Scanning Tunnelling Spectroscopic Studies of Dirac Fermions in Graphene and Topological Insulators

Yeh, N.-C. and Teague, M. L. and Wu, R. T.-P. and Chu, H. and Boyd, D. A. and Bockrath, M. W. and He, L. and Xiu, F.-X. and Wang, K.-L. (2012) Scanning Tunnelling Spectroscopic Studies of Dirac Fermions in Graphene and Topological Insulators. EPJ Web of Conferences, 23 . Art. No. 00021. ISSN 2101-6275. http://resolver.caltech.edu/CaltechAUTHORS:20120409-081805591

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Abstract

We report novel properties derived from scanning tunnelling spectroscopic (STS) studies of Dirac fermions in graphene and the surface state (SS) of a strong topological insulator (STI), Bi_2Se_3. For mono-layer graphene grown on Cu by chemical vapour deposition (CVD), strain-induced scalar and gauge potentials are manifested by the charging effects and the tunnelling conductance peaks at quantized energies, respectively. Additionally, spontaneous time-reversal symmetry breaking is evidenced by the alternating anti-localization and localization spectra associated with the zero-mode of two sublattices while global time-reversal symmetry is preserved under the presence of pseudo-magnetic fields. For Bi_2Se_3 epitaxial films grown on Si(111) by molecular beam epitaxy (MBE), spatially localized unitary impurity resonances with sensitive dependence on the energy difference between the Fermi level and the Dirac point are observed for samples thicker than 6 quintuple layers (QL). These findings are characteristic of the SS of a STI and are direct manifestation of strong topological protection against impurities. For samples thinner than 6-QL, STS studies reveal the openup of an energy gap in the SS due to overlaps of wave functions between the surface and interface layers. Additionally, spin-preserving quasiparticle interference wave-vectors are observed, which are consistent with the Rashba-like spin-orbit splitting.


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http://dx.doi.org/10.1051/epjconf/20122300021DOIUNSPECIFIED
Additional Information:© 2012 Owned by the authors, published by EDP Sciences. This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial License 3.0, which permits unrestricted use, distribution, and reproduction in any noncommercial medium, provided the original work is properly cited. Published online 07 March 2012. The research on graphene at Caltech was supported by the National Science Foundation, and the research on topological insulators at Caltech and UCLA was supported by the Center on Functional Engineered Nano Architectonics (FENA).
Group:Institute for Quantum Information and Matter, IQIM, Kavli Nanoscience Institute
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Center on Functional Engineered NanoArchitectonics (FENA)UNSPECIFIED
Record Number:CaltechAUTHORS:20120409-081805591
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20120409-081805591
Official Citation:Scanning Tunnelling Spectroscopic Studies of Dirac Fermions in Graphene and Topological Insulators N.-C. Yeh, M. L. Teague, R. T.-P. Wu, H. Chu, D. A. Boyd, M. W. Bockrath, L. He, F.-X. Xiu and K.-L. wang EPJ Web of Conferences 23 00021 (2012) DOI: http://dx.doi.org/10.1051/epjconf/20122300021
Usage Policy:This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial License 3.0, which permits unrestricted use, distribution, and reproduction in any noncommercial medium, provided the original work is properly cited.
ID Code:30030
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Apr 2012 21:49
Last Modified:26 Dec 2012 15:02

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