Extending classical computational electrodynamics to quantum domain

The Finite-Difference Time-Domain (FDTD) method [1] is widely used to simulate electromagnetic response of metallic structures, where abrupt boundary between materials is always assumed. However, when the scale is down to nanometer or even smaller, the non-abrupt electron density profile at metal surface causes problems, which are the so called nonlocal effects [2] (wavenumber-dependence) in plasmonics and nanophotonics research. We developed an approach [3] accounting for the non-abrupt surface profile, effectively extending the conventional FDTD method to nonlocal domain. This extension is still within the fast classical calculation scheme, but with the quantum mechanical surface plasmonic effects covered to first order. We utilized this approach to simulate on a few typical nanostructures, and the results on resonance shift and field enhancement agree very well with experiments and other ab initio calculations (e.g. DFT) in literature.

[1] Taflove and Hagness, Computational Electrodynamics (Artech, Norwood, MA, 1995)
[2] Raza, Bozhevolnyi, Wubs and Mortensen, J. Phys.: Condens. Matter 27, 183204 (2015)
[3] Kong, Shvonski and Kempa, Phys. Rev. B 97, 165423 (2018)