Condensed Matter Physics Seminar
Speaker: Eugene Mishchenko, University of Utah
Title: Many-body depolarization effect in metallic nanotubes
Refreshments available at 3:45 pm.
Date: Mon, 13 Nov 2017, 4:10 pm – 5:10 pm
Location: 1400 BPS Bldg.
In quasi-one-dimensional conducting systems, such as metallic carbon nanotubes, optical absorption properties are controlled by many-body effects. The band structure of such nanotubes originates from graphene folding, which splits the graphene pi-band into a set of subbands described by the azimuthal angular momentum m. In cases of metallic foldings, ensuing subband structure comprises both gapless (m=0) and gapped subbands (m≠0). Optical absorption for the polarization along the axis of the tube is determined by the exciton physics. Absorption of the perpendicular polarization is modified by the depolarization effect which reduces the magnitude of the electric field inside the tube Ei compared with the external field E0. In the classical electrostatic model, where a tube is replaced with a solid cylinder, the relation between the two fields is given by the textbook relation Ei = 2E0/(1+κ), in terms of the effective dielectric permittivity κ(ω). I will explain why this simple intuitive picture does not adequately describe absorption near its threshold, once many-body correlations are taken into account.