Condensed Matter Physics Seminar

Thursday, December 7, 2000, 2 p.m.
Plant Sciences Building, Room 1130

Unpaired Majorana fermions in quantum wires

Alexei Kitaev

(Microsoft Research and Landau Institute for Theoretical Physics)

Abstract:  Certain one-dimensional Fermi systems have an energy gap in the bulk spectrum while the boundary states are described by one Majorana operator per boundary point.  As a result, a finite system of length L posesses two ground states with different fermionic parity whose energy difference is proportional to exp(-L/a).  We find a general condition on the bulk electron spectrum which determines whether this situation is the case.  The condition is satisfied in the presense of arbitrary small energy gap induced by a 3-dimensional p-wave superconductor, provided that the original spectrum has an odd number of Fermi points in each half of the Brillouin zone (each spin component counts separately!).  Such systems can be used as qubits as they are intrinsically immune to decoherence.

Host: Victor Yakovenko

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