Contacts:
Martijn Wubs (Assoc. Prof.), DTU Fotonik, Building 345A room 172, Tel. 4525-6374,
mwubs@fotonik.dtu.dk
N. Asger Mortensen, (Prof.), DTU Fotonik, namo@fotonik.dtu.dk
Thomas Christensen, PhD student, DTU Fotonik, Building 343 room 129, tomch@fotonik.dtu.dk
It is only recently that graphene was discovered, a two-dimensional sheet of carbon (see Figure). It has many fascinating properties and possible applications, and it is therefore studied in many universities and companies all over the world. Also here at DTU!
(1) In this theoretical project we want to understand a few unique optical properties of graphene. These properties are tunable, since unlike for metals, the conductivity of graphene is tunable. We use multiple-scattering theory as our tool. It is an elegant theory that can become a way of thinking that helps you deepen your insight in many branches of physics, including quantum mechanics and
electromagnetism.
(2) The first goal is to study whether the theory predicts the existence of graphene plasmons, and if so what are their properties. Graphene plasmons are confined optical waves that travel along the graphene sheet. Goal number two is to find out how spontaneous-emission rates of emitters close to the graphene sheet are modified in a tunable way via the tunable conductivity. Your theoretical results can be directly compared to fascinating recent experiments in Nature [2].
(3) There is no need to start from scratch in this project, the challenge is rather to adapt an existing multiple-scattering theory [1] for dielectric sheets of matter to graphene. You will read introductory literature about graphene and about multiple-scattering theory. Your supervisors are happy to discuss with you to get you on track. You will get a flavor of pen-and-paper theoretical physics. So this is not a computer simulation project, although the computer will be certainly be used.
With this fagproject, you can make a kick-start into graphene research, and many researchers in the Center for Nanostructured Graphene (http://www.cng.dtu.dk/) will welcome you into the club. In our Structured Electromagnetic Materials Group (http://www.fotonik.dtu.dk/english/Research/Nanophotonics/SEM), we study nanophotonics both theoretically and experimentally, with special focus on graphene and metal plasmonics. Our many Group members can be a source of inspiration.
[1] M. Wubs, L. G. Suttorp, and A. Lagendijk, Spontaneous-emission rates in finite photonic crystals of plane scatterers, Physical Review E 69, 016616 (2004); see
http://www.martijnwubs.nl/publications/Wubs_PRE_69_016616_2004.pdf
[2] K. J. Tielrooij et al., Electrical control of optical emitter relaxation pathways enabled by graphene, Nature Physics, in press (2015); http://dx.doi.org/10.1038/NPHYS3204.
Artist impression of graphene, a two-dimensional sheet of carbon atoms arranged in a hexagonal lattice. By changing the number of electrons that can move freely within the sheet, the conductivity and also the optical properties of graphene can be controlled. Interestingly, light can travel in the form of confined optical waves along the surface ("graphene plasmons"). An optically excited atom close by graphene may emit light into such a graphene plasmon.