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Colloquium: Novel Phenomena Driven by Interactions and Symmetry-breaking in Graphene

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David Goldhaber-Gordon, Stanford University
When
13 November 2014 from 4:00 PM to 5:00 PM
Where
117 Osmond Laboratory
Contact Name
Nitin Samarth
Contact Phone
(814) 863-0136
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Ten years ago, it was amazing that a single atomic layer of carbon -- graphene -- could conduct electricity. Recent developments have led to graphene in which electrons flow more freely at room temperature than in any semiconductor 2D electron system. At low temperature, electrons can travel more than 10 microns without being deflected [1,2]. In these ultraclean samples, interactions and substrate-induced symmetry breaking lead to novel phenomena . I will speak about a few examples of such phenomena, including:
* Surprising insulating behavior at the charge neutrality point at zero magnetic field [3]
* Spin-selective equilibration of quantum Hall edge states [4]
* A large set of fractional quantum Hall states, at denominators up to 9, with 
unexpected patterns of stability and spin polarization [5]
* The key role of screening by a nearby gate electrode
[1] C. R. Dean, A. F. Young, I.Meric, C. Lee, L. Wang, S. Sorgenfrei, K. Watanabe, T. 
Taniguchi, P. Kim, K. L. Shepard and J. Hone, "Boron nitride substrates for high-
quality graphene electronics," Nature Nanotechnology 5 , 722 - 726 (2010) 
[2] Lei Wang, Inanc Meric, Pinshane Y. Huang, Qun Gao, Yuanda Gao, Helen Tran, 
Taniguchi Takashi, Watanabe Kenji, Luis M. Campos, David A. Muller, Jing Guo, Philip 
Kim, James Hone, Ken L. Shepard, Cory R. Dean
“One-Dimensional Electrical Contact to a Two-Dimensional Material"Science 342, 
614-617 (2013).
[3] F. Amet, J. R. Williams, K. Watanabe, T. Taniguchi, D. Goldhaber-
Gordon, "Insulating Behavior at the Neutrality Point in Single-Layer Graphene"
Physical Review Letters 110, 216601 (2013).
[4] F. Amet, J. R. Williams, K. Watanabe, T. Taniguchi, D. Goldhaber-
Gordon, "Gate control of spin and valley polarized quantum Hall edge states in 
graphene," Physical Review Letters 112, 196601 (2014).
[5] F. Amet, A. J. Bestwick, J. R. Williams, K. Watanabe, T. Taniguchi, D. Goldhaber-
Gordon Composite Fermions and Broken Symmetries in Graphene. arXiv/1410:3549.
To be published in Nature Communications.
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