Effects of Surface Morphology on the 3D Topological Insulator Samarium Hexaboride

ORAL

Abstract

The recent verification of a topologically-protected surface state in SmB$_6$ at low temperatures has led to several transport studies of the surface states. This task is complicated because current can flow on all surfaces of a topological insulator, each of which can have different transport characteristics. Our own measurements using a Corbino disc geometry overcome this difficulty, limiting the conduction to individual surfaces. However, the sheet conductivities of our samples counter-intuitively decrease with finer surface polishing. We therefore investigate surface and sub-surface morphology as a factor affecting the surface conductivity. Specifically, surface cracks may themselves harbor surface states and contribute to the total electrical conduction, yielding a higher measured sheet conductivity than that of a flat surface. This situation may contribute to the (sometimes unphysically) large surface conductivities already observed in SmB$_6$.

*Performed in part at the Lurie Nanofabrication Facility and the Electron Microbeam Analysis Laboratory. Funded by NSF grant \#DMR-1006500 and DMR-1441965. Thanks to Gang Li and Fan Yu for optical imaging.

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Authors

  • Steven Wolgast

    • Dept. of Physics, University of Michigan
    • Randall Laboratory of Physics, University of Michigan - Ann Arbor

  • Yun Suk Eo

    • Dept. of Physics, University of Michigan
    • Randall Laboratory of Physics, University of Michigan - Ann Arbor

  • Cagliyan Kurdak

    • Univ of Michigan - Ann Arbor
    • Dept. of Physics, University of Michigan
    • Randall Laboratory of Physics, University of Michigan - Ann Arbor

  • D. J. Kim

    • University of California at Irvine
    • Dept. of Physics and Astronomy, University of California, Irvine
    • University of California, Irvine

  • Z. Fisk

    • Univ of California - Irvine
    • Dept. of Physics and Astronomy, University of California, Irvine
    • University of California, Irvine