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Koumoulis D, Morris GD, He L, Kou X, King D, Wang D, Hossain MD, Wang KL, Fiete GA, Kanatzidis MG, Bouchard LS. Nanoscale β-nuclear magnetic resonance depth imaging of topological insulators. Proc Natl Acad Sci U S A 2015; 112:E3645-50. [PMID: 26124141 PMCID: PMC4507211 DOI: 10.1073/pnas.1502330112] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Considerable evidence suggests that variations in the properties of topological insulators (TIs) at the nanoscale and at interfaces can strongly affect the physics of topological materials. Therefore, a detailed understanding of surface states and interface coupling is crucial to the search for and applications of new topological phases of matter. Currently, no methods can provide depth profiling near surfaces or at interfaces of topologically inequivalent materials. Such a method could advance the study of interactions. Herein, we present a noninvasive depth-profiling technique based on β-detected NMR (β-NMR) spectroscopy of radioactive (8)Li(+) ions that can provide "one-dimensional imaging" in films of fixed thickness and generates nanoscale views of the electronic wavefunctions and magnetic order at topological surfaces and interfaces. By mapping the (8)Li nuclear resonance near the surface and 10-nm deep into the bulk of pure and Cr-doped bismuth antimony telluride films, we provide signatures related to the TI properties and their topological nontrivial characteristics that affect the electron-nuclear hyperfine field, the metallic shift, and magnetic order. These nanoscale variations in β-NMR parameters reflect the unconventional properties of the topological materials under study, and understanding the role of heterogeneities is expected to lead to the discovery of novel phenomena involving quantum materials.
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Affiliation(s)
- Dimitrios Koumoulis
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095
| | - Gerald D Morris
- TRI University Meson Facility (TRIUMF), Vancouver, BC, Canada V6T 2A3
| | - Liang He
- Department of Electrical Engineering, University of California, Los Angeles, CA 90095
| | - Xufeng Kou
- Department of Electrical Engineering, University of California, Los Angeles, CA 90095
| | - Danny King
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095
| | - Dong Wang
- Department of Physics & Astronomy, University of British Columbia, Vancouver, BC,Canada V6T 1Z1
| | - Masrur D Hossain
- TRI University Meson Facility (TRIUMF), Vancouver, BC, Canada V6T 2A3; Department of Physics & Astronomy, University of British Columbia, Vancouver, BC,Canada V6T 1Z1
| | - Kang L Wang
- Department of Electrical Engineering, University of California, Los Angeles, CA 90095
| | - Gregory A Fiete
- Department of Physics, University of Texas at Austin, Austin, TX 78712
| | | | - Louis-S Bouchard
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095; California NanoSystems Institute, University of California, Los Angeles, CA 90095
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