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Quasiparticle interference of the Fermi arcs and surface-bulk connectivity of a Weyl semimetal

Science  11 Mar 2016:
Vol. 351, Issue 6278, pp. 1184-1187
DOI: 10.1126/science.aad8766

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Sinking into the bulk of a Weyl semimetal

A recently discovered class of topological materials, Weyl semimetals, have surface states in the form of so-called Fermi arcs. Inoue et al. used a high-resolution scanning tunneling microscope to explore the properties of these states in the material TaAs. They mapped the scattering of electrons off impurities on the surface of the material and compared the data to the predictions of density functional theory. The data could be reconciled with the theory only if electrons associated with Ta orbitals on the Fermi arcs sank into the bulk of the material.

Science, this issue p. 1184

Abstract

Weyl semimetals host topologically protected surface states, with arced Fermi surface contours that are predicted to propagate through the bulk when their momentum matches that of the surface projections of the bulk’s Weyl nodes. We used spectroscopic mapping with a scanning tunneling microscope to visualize quasiparticle scattering and interference at the surface of the Weyl semimetal TaAs. Our measurements reveal 10 different scattering wave vectors, which can be understood and precisely reproduced with a theory that takes into account the shape, spin texture, and momentum-dependent propagation of the Fermi arc surface states into the bulk. Our findings provide evidence that Weyl nodes act as sinks for electron transport on the surface of these materials.

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