Marcel Franz

University of British Columbia
Self-organized topological state with Majorana fermions

Most physical systems known to date tend to resist entering the topological phase and must be fine tuned to reach the latter. In this talk I will introduce a system in which a key dynamical parameter adjusts itself in response to the changing external conditions so that the ground state naturally favors the topological phase. The system consists of a quantum wire formed of individual magnetic atoms placed on the surface of an ordinary s-wave superconductor. It realizes the Kitaev paradigm of topological superconductivity when the wavevector characterizing the emergent spin helix dynamically self-tunes to support the topological phase. We call this phenomenon self-organized topological state. Recent measurements in the Yazdani group show possible signatures of this phenomenon in chains of Gd atoms assembled on 110 surfaces of lead.

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