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Observation of chiral currents at the magnetic domain boundary of a topological insulator

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Science  28 Aug 2015:
Vol. 349, Issue 6251, pp. 948-952
DOI: 10.1126/science.aaa0508

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Magnetizing a topological insulator

Inducing magnetism in a topological insulator can lead to exotic effects. The usual experimental route is to introduce magnetic dopants into the material, but that approach is intricate and creates unwanted disorder. Wang et al. used a simpler technique: They fabricated a bilayer consisting of Bi2Se3, a topological insulator, and EuS, a magnet. The physical proximity of EuS induced magnetism on the surface of Bi2Se3. This approach allowed for the creation of magnetic domains at will and the detection of characteristic current flowing along the domains' edges.

Science, this issue p. 948

Abstract

A magnetic domain boundary on the surface of a three-dimensional topological insulator is predicted to host a chiral edge state, but direct demonstration is challenging. We used a scanning superconducting quantum interference device to show that current in a magnetized topological insulator heterostructure (EuS/Bi2Se3) flows at the edge when the Fermi level is gate-tuned to the surface band gap. We further induced micrometer-scale magnetic structures on the heterostructure and detected a chiral edge current at the magnetic domain boundary. The chirality of the current was determined by magnetization of the surrounding domain, and its magnitude by the local chemical potential rather than the applied current. Such magnetic structures provide a platform for detecting topological magnetoelectric effects and may enable progress in quantum information processing and spintronics.

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