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ICMT Seminar: "Twist Defects in Topological Systems with Symmetries"

SpeakerDr. Jeffrey Teo (University of Ilinois, Urbana-Champaign)
Date Oct 7, 2013
Time 12:00 pm  
Location 190 ESB
Sponsor Dept. of Physics
Contact Becky McDuffee
Phone 217-244-4268
Event type Seminar/Symposium
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Twist defects are point-like objects that support robust non-local storage of quantum information and non-abelian unitary operations. Unlike quantum deconfined anyonic excitations, they rely on symmetry rather than a non-abelian topological order. In this talk we explore two situations. (i) Majorana bound states (MBS) can arise at lattice defects, such as disclinations and dislocations, of a topological crystalline superconductor. MBS number parity is counted by a Z_2-topological index protected by bulk lattice symmetries. This predicts the appearance of MBS at lattice defects in superconducting strontium ruthenate and doped graphene. (ii) Twist defects in a symmetry enhanced topological phase, such as a bilayer fractional quantum Hall state and the Kitaev toric code, can carry (fractional) Ising-like properties. They are however fundamentally different from quantum anyonic excitations in a true topological phase. This is demonstrated by their unconventional exchange and braiding behavior, which is characterized by a modified spin statistics theorem and modular invariance.

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