Electron spin relaxation in semiconducting carbon nanotubes: the role of hyperfine interaction

TL;DR

This paper develops a theory for electron spin relaxation in semiconducting carbon nanotubes, highlighting the impact of hyperfine interactions with disordered nuclei and the unique temperature dependence due to one-dimensional electron density of states.

Contribution

It introduces a new theoretical model for spin relaxation in CNTs considering hyperfine interactions and predicts unusual temperature dependence of relaxation times.

Findings

Electron-nuclear overlap is enhanced by radial confinement.

Relaxation times decrease with increasing temperature.

Spin relaxation time in CNTs can reach about 1 second.

Abstract

A theory of electron spin relaxation in semiconducting carbon nanotubes is developed based on the hyperfine interaction with disordered nuclei spins I=1/2 of $^{13}$C isotopes. It is shown that strong radial confinement of electrons enhances the electron-nuclear overlap and subsequently electron spin relaxation (via the hyperfine interaction) in the carbon nanotubes. The analysis also reveals an unusual temperature dependence of longitudinal (spin-flip) and transversal (dephasing) relaxation times: the relaxation becomes weaker with the increasing temperature as a consequence of the particularities in the electron density of states inherent in one-dimensional structures. Numerical estimations indicate relatively high efficiency of this relaxation mechanism compared to the similar processes in bulk diamond. However, the anticipated spin relaxation time of the order of 1 s in CNTs is still much longer than those found in conventional semiconductor structures.