A number of groups have recently been active in searching for gradients in the observed Faraday rotation measure (RM) across jets of Active Galactic Nuclei (AGNs) on various scales and estimating their reliability. Such RM structures provide direct evidence for the presence of an azimuthal magnetic field component, which may be associated with a helical jet magnetic field, as is expected based on the results of many theoretical studies. We present new parsec-scale RM maps of 4 AGNs here, and analyze their transverse RM structures together with those for 5 previously published RM maps. All these jets display transverse RM gradients with significances of at least 3σ. This is part of an ongoing effort to establish how common transverse RM gradients that may be associated with helical or toroidal magnetic fields are in AGNs on parsec scales.

Previous studies have shown that incorporating a small fraction of carbon (C) into germanium (Ge) leads to the lowest conduction state being at the Γ point in small supercell calculations, suggesting that C incorporation can turn Ge into a direct gap semiconductor. We use hybrid functional density functional theory calculations as a function of hydrostatic pressure to investigate the nature (Γ-, X-or L-like) of the lowest conduction states in Ge 127 C 1 and Ge 63 C 1 supercells. We find in both cases that the lowest conduction state, at Γ in the supercell, has primarily L-like character. Surprisingly, the Ge Γ state mixes with a higher-lying X state, but has almost no interaction with the L-like conduction band edge state. We conclude that the band gap of the here studied Ge:C systems is therefore only quasi-direct, limiting the benefit of this material system for optoelectronic device applications.

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