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SUMMARY:Graphene and evidence for duality in quantum Hall systems - Cliff 
 Burgess (Perimeter)
DTSTART:20071031T141500Z
DTEND:20071031T153000Z
UID:TALK7917@talks.cam.ac.uk
CONTACT:Diego Hernan Correa
DESCRIPTION:Quantum Hall systems are characterized by a spectacular set of
 \nobservations (universal low-temperature conductivity\,\ncritical behavio
 ur and semi-circle laws for transitions\nbetween Quantum Hall states) that
  are more robust than\nwould be expected from the detailed theory of under
 lying\nelectron dynamics. The talk starts with a summary of these\nobserva
 tions\, and their derivation from the assumption\nthat the important charg
 e carriers at the low energies\nrelevant to conductivity measurements are 
 weakly\ninteracting particles or vortices. This implies a\nlarge emergent 
 duality symmetry (a level two subgroup of\nSL(2\,Z))\, whose presence unde
 rlies the robustness of the\nobservations in question. The newly-discovere
 d and unusual\nQuantum Hall properties of graphene are discussed as\nprovi
 ding a new test of this picture.
LOCATION:MR2\, Centre for Mathematical Sciences
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