Binding energy and lifetime of excitons in metallic nanotubes

Abstract

The difficulty of describing excitons in semiconducting single-wall nanotubes analytically lies with the fact that excitons can neither be considered strictly one-nor two-dimensional objects. However, the situation changes in the case of metallic nanotubes where, by virtue of screening from gapless metallic subbands, the radius of the exciton becomes much larger than the radius of the nanotube Rex ≫ R. Taking advantage of this, we develop the theory of excitons in metallic nanotubes, determining that their binding energy is about 0.08v/R, in agreement with the existing experimental data. Additionally, because of the presence of the gapless subbands, there are processes where bound excitons are scattered into unbound electron-hole pairs belonging to the gapless subbands. Such processes lead to a finite exciton lifetime and the broadening of its spectral function. We calculate the corresponding decay rate of the excitons.

Optical properties of core/shell spherical quantum dots*

“…[11][12][13][14] Generally speaking, because excitons can show the electrical and optical properties of quantum dots to a certain extent, many people have done research on excitons in both experiment and theory. [15][16][17] Chafai et al [18] used the variational method to predict that in the spherical GaN/AlN core/shell quantum dot, the external electric field will reduce the binding energy of exciton state, and the increase of quantum dot size will also reduce the binding energy. Pattammal et al [19] studied the influence of well width on exciton radiation life-time in InGaN/GaN quantum wires.…”