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SUMMARY:Graphene: the good\, the bad\, and the beauty - Prof. Christiane M
 orais Smith\, University of Utrecht
DTSTART:20150507T131500Z
DTEND:20150507T144500Z
UID:TALK58514@talks.cam.ac.uk
CONTACT:Dr G Moller
DESCRIPTION:Graphene is probably the most fascinating material ever discov
 ered\, but it has some drawbacks: it is not superconducting\, it does not 
 exhibit the quantum spin Hall effect\, and its magnetic properties are sti
 ll controversial. The interesting electronic properties of graphene\, such
  as the presence of charge carriers that behave as if they would have no m
 ass\, are rooted on the honeycomb lattice of the carbon atoms. This insigh
 t provides a unique opportunity: by creating honeycomb lattices of materia
 ls other than carbon\, the effects conferred by the atoms can be combined 
 with those conferred by the honeycomb lattice and novel materials\, with u
 nexpected properties\, may emerge. A key question in this regard is: if we
  build a honeycomb lattice out of semiconducting nanocrystals\, is it goin
 g to behave like graphene or like the semiconducting building blocks? \n\n
 In the first part of the talk\, I will show that these systems\, which hav
 e been experimentally synthesized last year [1]\, combine the best of the 
 two materials. Honeycomb lattices of semiconducting nanocrystals exhibit a
  gap at zero energy\, as well as Dirac cones are finite energies. In addit
 ion\, a honeycomb lattice made of CdSe nanocrystals displays \ntopological
  properties in the valence band [2]\, whereas for HgTe very large topologi
 cal gaps are predicted to occur in the conduction p-bands [3]. These artif
 icial materials thus open the possibility to engineer higher-orbital physi
 cs with Dirac electrons and to realize quantum (spin) Hall phases at room 
 temperature [3].  \n\nIn the second part of the talk\, I will discuss how 
 to describe the full dynamical electromagnetic interaction in 2D systems l
 ike graphene\, where the electrons are constrained to move in the 2D plane
 \, whereas the photons move in 3D. By using the so-called pseudo-QED appro
 ach\, I will show how quantized edge states emerge in this system and give
  rise to the quantum Valley Hall Effect [4]\, thus opening the possibility
  to realize Valleytronics as an alternative to Spintronics and Electronics
 . \n\n[1] M. P. Boneschanscher et al\, Science 344\, 1377 (2014).\n[2] E. 
 Kalesaki\, C. Delerue\, C. Morais Smith\, W. Beugeling\, A. Allan\, and D.
  Vanmaekelbergh\, Phys. Rev. X 4\, 011010 (2014).\n[3] W. Beugeling\, E. K
 alesaki\, C. Delerue\, Y.-M. Niquet\, D. Vanmaekelbergh\, and C. Morais Sm
 ith\, Nature Communications 6\, 6316 (2015).\n[4] E. Marino\, L. O. Nascim
 ento\, V. S. Alves\, and C. Morais Smith\, Phys. Rev. X 5\, (2015).
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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