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MA: Fachverband Magnetismus

MA 19: Transport: Topological Semimetals 1 (jointly with DS, MA, HL, O)

MA 19.1: Vortrag

Dienstag, 21. März 2017, 09:30–09:45, HSZ 201

Electron-hole pairing of Fermi arc surface states in a Weyl semimetal bilayer — •Paolo Michetti and Carsten Timm — Institute of Theoretical Physics, Technische Universität Dresden, 01062 Dresden, Germany

The topological nature of Weyl semimetals (WSMs) is corroborated by the presence of chiral surface states at the boundaries, connecting the bulk Fermi surface by Fermi arcs (FAs). We develop an analysis of the electron-hole pairing instability between the surface states of a bilayer structure realized by introducing a thin insulating spacer into a bulk WSM. We employ a minimal WSM model for the description of the surface states and a self-consistent mean-field treatment of the pairing interaction. We find that the system is unstable towards the formation of coherent electron-hole pairs, which leads to partial gapping of the FA dispersion curve and possibly to a superfluid dipolar exciton condensate, where dissipationless counter-propagating currents can be induced in the two layers. A signature of such condensate is the modifications of the peculiar quantum oscillations from surface FAs. We characterize the dependence of the single-particle energy gap and the critical temperature on the model parameters, where we emphasize in particular the linear scaling of these quantities with the separation between the Weyl points. A detrimental role is played by the curvature of the FA, although the phenomenon persists for moderately low curvature.