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SUMMARY:Landau level spectroscopy reveals the chirality and Klein tunnelli
 ng of electrons in twisted graphene tunnel transistors - Dr Mark Greenaway
 \, Nottingham University
DTSTART:20160125T141500Z
DTEND:20160125T151500Z
UID:TALK63986@talks.cam.ac.uk
CONTACT:Teri Bartlett
DESCRIPTION:Multilayer transistors based on graphene and other van der Waa
 ls crystals exhibit interesting physical properties\, high on-off current 
 switching ratios\, mechanical flexibility and resonant tunnelling with\nga
 te voltage-tuneable negative differential conductance at room temperature 
 [1-3]. In these devices\, we have recently demonstrated the strong sensiti
 vity of in-plane momentum conserving tunnel transitions to any small misal
 ignment or twist angle between the crystalline lattices of the two graphen
 e electrodes [4]. Following a brief review of this recent work\, we will p
 resent new results which investigate the effect of a magnetic field applie
 d perpendicular to the graphene layers on the current-voltage characterist
 ics of devices in which the graphene lattices are carefully aligned to wit
 hin 1 degree. The magnetic field quantises the electronic states in the co
 nical\, gapless conduction and valence bands into a ladder of unequally-sp
 aced Landau levels.\n\nTunnelling of electrons between the Landau levels o
 f the two graphene electrodes gives rise to a complex pattern of sharp res
 onant peaks in the differential conductance (dI/dV). To analyse these data
 \, we use a\nBardeen transfer Hamiltonian approach which incorporates the 
 two-component spinor-spatial character of the Dirac-Weyl fermions. We demo
 nstrate how the intensity of the energy- and momentum- conserving tunnel t
 ransitions reveal the effects of chirality [5]\, which is a unique feature
  of electron dynamics in graphene and related materials.\n\n[1] L. Britnel
 l et al.\, Science 335\, 947 (2012).\n[2] T. Georgiou et al.\, Nature Nano
 technology 2\, 100 (2013).\n[3] L. Britnell et al.\, Nature Communications
  4\, 1794 (2013).\n[4] A. Mishchenko et al.\, Nature Nanotechnology 9\, 80
 8 (2014).\n[5] M. Greenaway et al.\, Nature Physics 11\, 1057 (2015).\n
LOCATION:Ryle Seminar Room no. 930\, Rutherford Building\, Cavendish Labor
 atory
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