Neoclassical theory of electromagnetic interactions for nanoplasmonics and plasma physics

Monday, December 12, 2016 - 10:30am - 11:30am
Keller 3-180
Alexander Figotin (University of California, Irvine)
Remarkable advances made in studies of man-made electromagnetic materials (metamaterials) pose new challenges for the theory of electromagnetic interaction. Particularly the studies of metamaterials associated with nanoscale stimulated further theoretical developments of a number of subjects such as plasmonics, plasma physics and electron emission theory.
In this presentation we provide a concise exposition of our recently developed neoclassical theory and its applications to the above mentioned subjects. Our neoclassical theory features a new spatial scale - the size a_{e} of a free electron. This scale is special to our theory and does not appear in either classical EM theory nor in the quantum mechanics where electron is always a point-like object. Our current assessed value for this scale is a_{e}≈100a_{B} where a_{B} is the Bohr radius, and consequently a_{e}≈5 nm. In our theory any elementary charge is a distributed in space quantity. Its size is understood as the localization radius which can vary depending on the situation. For instance, if an electron is bound to a proton in the Hydrogen atom then its the size of is approximately 1 Bohr radius, that is a_{B}≈0.05 nm, and when the electron is free its size is a_{e}≈100a_{B}≈5 nm.
Plasmonic resonance responses have spatial dimension ranging between 1 nm and 25 nm. We entertain an idea that the very existence of surface plasmons with sizes in that range suggest their relation to the new fundamental scale - the size 5nm of a free electron in our neoclassical theory. Interestingly, the upper bound 25 nm is the skin depth and that implies that a nanosystem of size smaller than 25 nm is transparent to the external field. The same transparency should hold for a nanostructured surface indicating such a surface is better for nearly ideal field electron emission. There is an experimental evidence showing that the highest current densities were obtained for nanotips with sizes ∼ 1nm yet another important fact supporting a possibility of a new fundamental nanoscale.