Eliminating the effects of the pesky bulk

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Science  29 Aug 2014:
Vol. 345, Issue 6200, pp. 1017
DOI: 10.1126/science.345.6200.1017-c

A material's imperfections can greatly influence how well it conducts electricity. Theoretical physicists have, however, come up with the concept of topological insulators (TIs): materials that conduct only at their surface in a way that makes them “immune” to certain kinds of disorder. The compounds that have been identified as TIs, such as Bi2Se3, fall short of this ideal because they conduct electricity both through the “immune” surface states and the bulk of the material, which is still affected by disorder. Brahlek et al. made thin samples of Bi2Se3, adding copper atoms in precise quantities. When the samples were thick enough and had just the right concentrations of copper, the authors found that the samples were conducting only at their surfaces. This work is a step forward toward making useful TI devices.

Phys. Rev. Lett. 113, 026801 (2014).

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