RT Journal Article
SR Electronic
T1 Tunable intraband optical conductivity and polarization-dependent epsilon-near-zero behavior in black phosphorus
JF Science Advances
JO Sci Adv
FD American Association for the Advancement of Science
SP eabd4623
DO 10.1126/sciadv.abd4623
VO 7
IS 2
A1 Biswas, Souvik
A1 Whitney, William S.
A1 Grajower, Meir Y.
A1 Watanabe, Kenji
A1 Taniguchi, Takashi
A1 Bechtel, Hans A.
A1 Rossman, George R.
A1 Atwater, Harry A.
YR 2021
UL http://advances.sciencemag.org/content/7/2/eabd4623.abstract
AB 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.