Phys. Rev. Lett. 109, 126806 (2012)

Nanoparticles scatter light that has a wavelength of the same order of magnitude as their diameter. In semiconductors, conduction electrons have a typical wavelength of 0.1 to 10 nm and therefore most nanoparticles will scatter them. Gang Chen and colleagues at MIT have now proposed a way to prevent this from happening and describe scenarios in which nanoparticles can be used to control the propagation of conduction electrons and thus act as filters or switches.

To make nanoparticles invisible to conducting electrons — a phenomenon known as electron cloaking — all that is needed is core–shell nanoparticles. The potential well and barrier associated with the shell and core of the nanoparticle can be made to minimize the scattering amplitude of the first two partial waves (those with an angular momentum of zero and one), which contribute the most to the total scattering cross-section. Under the right conditions, electrons within just a few tens of electronvolts of energy difference will 'see' only 0.01% of the nanoparticle in front of them. By tuning variables such as the mass of the nanoparticle's core and shell, and potential heights, it is possible to control the cloaking capabilities of the system.