arXiv subjects

H. M. Lawler

Publications and source records attributed to H. M. Lawler.

2 recordsLinked to original sources

arXiv2008

Optical to UV spectra and birefringence of SiO$_2$ and TiO$_2$: First-principles calculations with excitonic effects

A first principles approach is presented for calculations of optical -- ultraviolet (UV) spectra including excitonic effects. The approach is based on Bethe-Salpeter equation calculations using the \textsc{NBSE} code combined with ground-state density-functional theory calculations from the electronic structure code \textsc{ABINIT}. Test calculations for bulk Si are presented, and the approach is illustrated with calculations of the optical spectra and birefringence of $α$-phase SiO$_2$ and the rutile and anatase phases of TiO$_2$. An interpretation of the strong birefringence in TiO$_2$ is presented.

cond-mat.mtrl-sci↗

arXiv2007

Room-temperature ballistic transport in narrow graphene strips

We investigate electron-phonon couplings, scattering rates, and mean free paths in zigzag-edge graphene strips with widths of the order of 10 nm. Our calculations for these graphene nanostrips show both the expected similarity with single-wall carbon nanotubes (SWNTs) and the suppression of the electron-phonon scattering due to a Dirichlet boundary condition that prohibits one major backscattering channel present in SWNTs. Low-energy acoustic phonon scattering is exponentially small at room temperature due to the large phonon wave vector required for backscattering. We find within our model that the electron-phonon mean free path is proportional to the width of the nanostrip and is approximately 70 $μ$m for an 11-nm-wide nanostrip.

cond-mat.mes-hall↗