|Description||Alexey Belyanin, Ph.D.|
Department of Physics and Astronomy
Texas A&M University
“Nonlinear Optics of Graphene and Topological Insulators”
Graphene holds many records related to its mechanical, thermal, electrical, and optical properties. In this talk we add yet another distinction to this list of superlatives: we predict that graphene possesses a giant mid/far-infrared optical nonlinearity, perhaps the highest among known materials. It originates from unusual properties of electron states and selection rules for the optical transitions near the Dirac point, where the conduction and valence bands touch each other, forming a cone in the momentum space. A similar Dirac cone exists in the electronic structure of surface states in topological insulators. These states attracted a lot of interest, although the main effort was directed at studying their transport properties and spin-orbit interaction. Here we argue that the nonlinear optical properties of topological insulators are equally exciting. Moreover, we show that the optical nonlinearity of massless Dirac fermions in graphene and topological insulators can be further enhanced by coupling to surface plasmons and by applying a magnetic field. Giant optical nonlinearity enables generation of coherent mid-infrared and THz radiation through resonant difference-frequency generation, four-wave mixing, and Raman scattering. Another interesting application is the generation of polarization-entangled light. Unique nonlinear properties of Dirac fermions enable schemes with a high signal to noise ratio and high generation rate of entangled photons. They also open an interesting possibility of detection and control of electron states near the Dirac point by means of nonlinear optics.
 X. Yao and A. Belyanin, Giant optical nonlinearity of graphene in a strong magnetic field, Phys. Rev. Lett. 108, 255503 (2012)
 M. Tokman, X. Yao and A. Belyanin, Generation of entangled states in graphene in a strong magnetic field, arXiv 1209.1532; Phys. Rev. Lett. 110, 0774904 (2013).
 X. Yao, M. Tokman, and A. Belyanin, Plasmon-enhanced generation of THz radiation in graphene and topological insulators, in preparation.
For more information contact: Dr. Anzhong Wang 254-710-2276