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SUMMARY:Topological order from parafermions - Paul Fendley\, Oxford Univer
 sity\, All Souls College
DTSTART:20150212T141500Z
DTEND:20150212T151500Z
UID:TALK57134@talks.cam.ac.uk
CONTACT:Dr G Moller
DESCRIPTION:Much effort has been devoted to the study of systems with\ntop
 ological order\, motivated by practical issues as well as more\nfield-theo
 retical and mathematical concerns. A sign of topological order in a\ngappe
 d one-dimensional quantum chain is the existence of edge zero modes.\nThes
 e occur in the Z_2-invariant Ising/Majorana chain\, where they can be\nund
 erstood using free-fermion techniques. Here I show they also occur in\nstr
 ongly interacting spin chains with Z_n symmetry\, and are naturally\nexpre
 ssed in terms of parafermions. Strikingly\, these edge zero modes do not\n
 occur in the usual ferromagnetic and antiferromagnetic cases\, but rather 
 only\nwhen the interactions are chiral\, so that spatial-parity and time-r
 eversal\nsymmetries are broken. I will also discuss how some of these idea
 s\ncan be applied profitably to two-dimensional models.\n
LOCATION:TCM Seminar Room\, Cavendish Laboratory\, Department of Physics
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