Schedule Sep 14, 2016
Strong zero modes: what they are and what they're good for
Paul Fendley, Univ. of Oxford & KITP

Robust edge zero modes guaranteeing ground-state degeneracy are common in a topological phase of matter. A more dramatic effect occurs in the Ising/Majorana/Kitaev chain: "strong" edge zero modes result in identical spectra in the entire even and odd fermion-number sectors, up to exponentially small finite-size corrections. A strong zero mode in a clean system is not a free-fermionic fluke. In the XYZ chain/coupled Majorana wires, its presence guarantees infinite coherence time for the edge spin, even with an infinite-temperature initial state. In non-integrable systems like the Ising chain with four-fermion interactions, an "almost" strong zero mode results in a very long coherence time, falling off very slowly with system size.

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