Thin-film topological insulators for continuously tunable terahertz absorption

Journal Article · Tue Feb 27 00:00:00 EST 2018 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.5016803· OSTI ID:1540154

West, D. ^[1]; Zhang, S. B. ^[1]

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1. Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Physics, Applied Physics, and Astronomy

One of the defining characteristics of a three-dimensional topological insulator (TI) is the appearance of a Dirac cone on its surface when it creates an interface with vacuum. For thin film TIs, however, the Dirac cones on opposite surfaces interact forming a small gap. For the case of three quintuple layers of Bi₂Se₃, we show that this gap can be continuously tuned between 128 meV and 0 meV with the application of modest perpendicular electric fields of less than 30 meV Å^-1. With both the Hamiltonian model and first-principles density functional theory calculations, we show that the inherent nonlinearity in realistic Dirac cone interaction leads to a gap which can be continuously tuned through the application of an external electric field. This tunability, coupled with the high optical absorption of thin film TIs, make this a very promising platform for terahertz and infrared detection.

• Research Organization: Rensselaer Polytechnic Inst., Troy, NY (United States); Univ. of California, Oakland, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: SC0002623; AC02-05CH11231; DESC0002623
• OSTI ID: 1540154
• Alternate ID(s): OSTI ID: 1422862
• Journal Information: Applied Physics Letters, Vol. 112, Issue 9; ISSN 0003-6951
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

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