Electron polarization and plasmon effects in anisotropic nanostructures

Properties of nanorods with the length 2 a and radius b (a > b), containing free carriers, in the external d.c. or a. c. electric field are analyzed theoretically. Static polarizability of nanorods depends on their orientation in the field and is determined by the ratio, the nanorod size in the field direction to the screening length of the material r(s). When this ratio is very small or very large, the properties of nanorods are similar to those of a dielectric and metallic ellipsoid, respectively. For a >> b, polarization characteristics of nanorods are strongly anisotropic and can be metallic in one direction and dielectric in the other direction. For semiconductor nanorods suspended in a polar liquid, polarizability in different directions may have different signs. For a. c. field, conductivity of nanorods contains plasmon peaks with essentially different frequencies for longitudinal and transverse plasmons. With decreasing a and b, frequencies of both plasmons increase and their amplitudes dramatically decrease. Dynamics of conducting nanorods in external electric fields represents superposition of their angular alignment along the field direction and the drift motion in the field gradient, with the first process being faster. Thus, in non-uniform fields nanorods drift in the field gradient according to the signs and values of their longitudinal and transverse polarizations. (C) 2013 AIP Publishing LLC.