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SUMMARY:Quantum Ice - Dr Nic Shannon\, University of Bristol
DTSTART:20110217T141500Z
DTEND:20110217T151500Z
UID:TALK28207@talks.cam.ac.uk
CONTACT:Dr G Moller
DESCRIPTION:Fractional excitations are well known in one dimension\, in po
 lyacetylene\, and in two dimensions\, in the fractional quantum Hall effec
 t.   It was widely believed that three-dimensional models could not suppor
 t fractional excitations\, since the fractionalization of charge in one- a
 nd two-dimensional electronic liquids seemed to be intimately linked to th
 e fractional quantum statistics found in lower dimension. \n\nRecently\, h
 owever\, a spectacular example of fractionalization in \nthree dimensions 
 has emerged\, in the form of magnetic monopoles in spin ice [1\,2].  These
  monopoles act as independent\, point-like sources of magnetic field\, and
  as such are deconfined\, fractional excitations.   But they are also\, by
  construction\, classical entities.\n\nIn this talk I present numerical ev
 idence that a closely related class of three-dimensional quantum models ca
 n also support such fractional excitations in three dimensions [3].  The m
 ost interesting of these models is a ``quantum ice'' which provides a desc
 ription of the tunneling of protons in water ice or\, equivalently\, the q
 uantum dynamics at low temperature in spin ice.\n\n[1]  C. Castelnovo et a
 l.\, Nature (London) 451\, 42 (2008)\n[2]  S. Bramwell et al.\, Nature (Lo
 ndon) 461\, 956 (2009)\n[3]  O. Sikora et al.\, Phys. Rev. Lett. 103\, 247
 001 (2009)
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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