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Published January 8, 2021 | Published + Submitted + Supplemental Material
Journal Article Open

Tunable intraband optical conductivity and polarization-dependent epsilon-near-zero behavior in black phosphorus


Black phosphorus (BP) offers considerable promise for infrared and visible photonics. Efficient tuning of the bandgap and higher subbands in BP by modulation of the Fermi level or application of vertical electric fields has been previously demonstrated, allowing electrical control of its above-bandgap optical properties. Here, we report modulation of the optical conductivity below the bandgap (5 to 15 μm) by tuning the charge density in a two-dimensional electron gas induced in BP, thereby modifying its free carrier–dominated intraband response. With a moderate doping density of 7 × 10¹² cm⁻², we were able to observe a polarization-dependent epsilon-near-zero behavior in the dielectric permittivity of BP. The intraband polarization sensitivity is intimately linked to the difference in effective fermionic masses along the two crystallographic directions, as confirmed by our measurements. Our results suggest the potential of multilayer BP to allow new optical functions for emerging photonics applications.

Additional Information

© 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Submitted 22 June 2020; Accepted 18 November 2020; Published 8 January 2021. We thank Q. Guo regarding preliminary discussions about this project, J. Wong for discussions regarding transfer matrices, G. K. Shirmanesh for help with printed circuit boards for electrical measurements, and L. Kim for providing LabVIEW script to perform electrical measurements. We acknowledge support from the Department of Energy–Office of Science under grant DE-FG02-07ER46405. This research used resources of the Advanced Light Source, a U.S. DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, grant number JPMXP0112101001, JSPS KAKENHI grant number JP20H00354, and the CREST (JPMJCR15F3), JST. Author contributions: S.B., W.S.W., and H.A.A. conceived the project. S.B. and W.S.W. worked on fabrication, measurements, and analysis of preliminary data. S.B. fabricated, measured, and analyzed data from final samples. M.Y.G. assisted in electrical and optical measurements. S.B., W.S.W., and M.Y.G. discussed the implications of the results. H.A.A. supervised the project. H.A.B. assisted with additional and complementary measurements done at the ALS, Berkeley. K.W. and T.T. provided hBN and BP crystals. G.R.R. supervised some of the optical measurements. S.B. wrote the manuscript, and all authors provided important feedback. The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.

Attached Files

Published - eabd4623.full.pdf

Submitted - 2009.00856.pdf

Supplemental Material - abd4623_SM.pdf


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August 22, 2023
October 20, 2023