Title: From Half-metal to Semiconductor: Electron-correlation Effects in Zigzag SiC Nanoribbons From First Principles,
Abstract: We performed electronic structure calculations based on the first-principles
many-body theory approach in order to study quasiparticle band gaps, and
optical absorption spectra of hydrogen-passivated zigzag SiC nanoribbons.
Self-energy corrections are included using the GW approximation, and excitonic
effects are included using the Bethe-Salpeter equation. We have systematically
studied nanoribbons that have widths between 0.6 $\text{nm}$ and 2.2
$\text{nm}$. Quasiparticle corrections widened the Kohn-Sham band gaps because
of enhanced interaction effects, caused by reduced dimensionality. Zigzag SiC
nanoribbons with widths larger than 1 nm, exhibit half-metallicity at the
mean-field level. The self-energy corrections increased band gaps
substantially, thereby transforming the half-metallic zigzag SiC nanoribbons,
to narrow gap spin-polarized semiconductors. Optical absorption spectra of
these nanoribbons get dramatically modified upon inclusion of electron-hole
interactions, and the narrowest ribbon exhibits strongly bound excitons, with
binding energy of 2.1 eV. Thus, the narrowest zigzag SiC nanoribbon has the
potential to be used in optoelectronic devices operating in the IR region of
the spectrum, while the broader ones, exhibiting spin polarization, can be
utilized in spintronic applications.