Two-dimensional (2D) materials provide a platform for strong light-matter interactions, creating wide-ranging design opportunities via new-material discoveries and new methods for geometrical structuring. We derive general upper bounds to the strength of such light-matter interactions, given only the optical conductivity of the material, including spatial nonlocality, and otherwise independent of shape and configuration. Our material figure-of-merit shows that highly doped graphene is an optimal material at infrared frequencies, whereas single-atomic-layer silver is optimal in the visible. For quantities ranging from absorption and scattering to near-field spontaneous-emission enhancements and radiative heat transfer, we consider canonical geometrical structures and show that in certain cases the bounds can be approached, while in others there may be significant opportunity for design improvement. The bounds can encourage systematic improvements in the design of ultrathin broadband absorbers, 2D antennas, and near-field energy harvesters.
Bibliographical noteFunding Information:
O.D.M. was supported by the Air Force Office of Scientific Research under award number FA9550-17-1-0093. O.I. and H.A.A. were supported as part of the DOE “Light-Material Interactions in Energy Conversion Energy Frontier Research Center under Grant DE-SC0001293 and acknowledge support from the Northrop Grumman Corporation through NG Next. T.C. was supported by the Danish Council for Independent Research (Grant DFFC6108-00667). M.S. was partly supported (reading and analysis of the manuscript) by S3TEC, an Energy Frontier Research Center funded by the U.S. Department of Energy under Grant DE-SC0001299. J.D.J., M.S., and S.G.J. were partly supported by the Army Research Office through the Institute for Soldier Nanotechnologies under Contract W911NF-13-D-0001.
- 2D materials
- near-field optics
- upper bounds