|Title:||Excitation Spectra of 2D Massless Dirac Fermion Systems: Graphene and Topological Insulators|
|Speaker:||Louie, Steven G.|
|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. 12|
Title from title slide.
Host: Institute for Advanced Study.
Sponsor: The Collaborative Research Fund (CRF), The Research Grants Council (RGC).
Abstract: The speaker presents results of some recent theoretical studies on the electronic excitation spectra associated with the 2D massless Dirac fermions in graphene and topological insulators. These systems present a new opportunity for study of unusual manifestation of concepts/phenomena that may not be so prominent or have not been seen in bulk materials. For doped graphene, angle-resolved photoemission experiments reveal that there is an intriguing satellite peak in the measured spectra, in addition to the expected quasiparticle peak. The question remains whether this satellite peak is, as suggested previously, due to a new elementary excitation - the plasmaron. By combining the ab initio GW method with cumulant expansion (thus including significant vertex corrections), our first-principles results explain the observed satellite properties in terms of coupling to the carrier plasmons, but do not find existence of plasmarons (defined as excitations that are solutions to the Dyson's equation). For topological insulators, we show that the degree of spin polarization of photoelectrons from the topologically protected surface states is 100% if fully polarized light is used as in typical photoemission measurements, and, hence, can be significantly higher than that of the initial state. Moreover, we find that the spin orientation of these photoelectrons in general can be very different from that of the initial surface state and is controlled by the photon polarization.
Duration: 40 min.
|Appears in Series:||8.15:3 - Audio-visual Materials|
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