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Title: Anomalous Properties of Dirac Particles in Graphene and Its Multilayers
Originating Office: IAS
Speaker: Koshino, Mikito
Issue Date: 15-Dec-2012
Event Date: 15-Dec-2012
Group/Series/Folder: Record Group 8.15 - Institute for Advanced Study
Series 3 - Audio-visual Materials
Location: 8.15:3 box 1.8
Notes: IAS Asia Pacific Workshop on Condensed Matter Physics. Talk no. 19
Title from title slide.
Host: Institute for Advanced Study.
Sponsor: The Collaborative Research Fund (CRF), The Research Grants Council (RGC).
Abstract: Graphene is characterized with Dirac quasiparticles in the low-energy spectrum, which give rise to anomalous physical properties due to the linear dispersion and non-trivial Berry phase. One of the manifestations of the unusual band structure is anomalous orbital diamagnetism, where the susceptibility has a singularity expressed as a delta function in Fermi energy, which diverges at Dirac point and vanishes otherwise. The singular diamagnetism is closely related to the scale-less property of the electronic structure, and we can show that the delta-function susceptibility is always concluded in any systems as long as the Hamiltonian is linear to the wave number. The scale-less electronic structure also manifests itself in response to non-uniform magnetic fields, where graphene works as a magnetic mirror, i.e., the counter magnetic field induced by graphene perfectly copies the external field distribution. There are growing interests in multilayer variants of graphene such as bilayer and trilayer, which also support chiral quasiparticles. We study the electronic structures of Bernal(AB) stacked multilayer graphenes in the presence of uniform perpendicular electric field, and show that the interplay of the trigonal warping and the external electric field gives rise to a number of additional Dirac cones nearly touching at zero energy. In Bernal trilayer graphene, in particular, we find that non-trivial valley Hall state is realized by applying the electric field, where the energy gap is filled by the chiral edge channels counter-propagating between two valleys. We show that the non-trivial valley Hall state generally occurs in odd layer graphenes with electric field, and this is closely related to a hidden approximate chiral symmetry which exists only in odd layer graphene.
Duration: 36 min.
Appears in Series:8.15:3 - Audio-visual Materials
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