Suspended semiconductor nanostructures: physics and technology

The current state of research on quantum and ballistic electron transport in semiconductor nanostructures with a two-dimensional electron gas separated from the substrate and nanoelectromechanical systems is reviewed. These nanostructures fabricated using the surface nanomachining technique have certain unexpected features in comparison to their non-suspended counterparts, such as additional mechanical degrees of freedom, enhanced electron-electron interaction and weak heat sink. Moreover, their mechanical functionality can be used as an additional tool for studying the electron transport, complementary to the ordinary electrical measurements. The article includes a comprehensive review of spin-dependent electron transport and multichannel effects in suspended quantum point contacts, ballistic and adiabatic transport in suspended nanostructures, as well as investigations on nanoelectromechanical systems. We aim to provide an overview of the state-of-the-art in suspended semiconductor nanostructures and their applications in nanoelectronics, spintronics and emerging quantum technologies

Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre

We provide an updated assessment of the power of the Cherenkov Telescope Array (CTA) to search for thermally produced dark matter at the TeV scale, via the associated gamma-ray signal from pair-annihilating dark matter particles in the region around the Galactic centre. We find that CTA will open a new window of discovery potential, significantly extending the range of robustly testable models given a standard cuspy profile of the dark matter density distribution. Importantly, even for a cored profile, the projected sensitivity of CTA will be sufficient to probe various well-motivated models of thermally produced dark matter at the TeV scale. This is due to CTA's unprecedented sensitivity, angular and energy resolutions, and the planned observational strategy. The survey of the inner Galaxy will cover a much larger region than corresponding previous observational campaigns with imaging atmospheric Cherenkov telescopes. CTA will map with unprecedented precision the large-scale diffuse emission in high-energy gamma rays, constituting a background for dark matter searches for which we adopt state-of-the-art models based on current data. Throughout our analysis, we use up-to-date event reconstruction Monte Carlo tools developed by the CTA consortium, and pay special attention to quantifying the level of instrumental systematic uncertainties, as well as background template systematic errors, required to probe thermally produced dark matter at these energies

Electrochemical behaviour of oligometallic sandwich complexes of cyclosiloxanolate ligands

The conductometric and voltammetric behaviour of 16 oligocyclosiloxanolate transition metal complexes in DMF is reported and discussed. The results of the conductometric measurements indicate that in DMF most of the compounds are electrolytes and the conductivity is due prevalently to the mobile (free) Na+ cation, the contribution of the large cluster anion being negligible, The cyclic voltammetric curves show only one reversible peak couple with E-p values very close to each other. These results suggest a high extent of electronic delocalisation in the cluster core of these sandwich type complexes and permit these compounds to be regarded as heteronuclear clusters of higher-valent transition metals

Cyclosiloxane sandwich complexes of a lanthanide metal: Na-6{[(C6H5SiO2)(8)](2)Nd-4(mu(4)-O)}

The oligocyclosiloxane cluster ('sandwich') complex of Nd3+, Na-6{[(C6H5SiO2)(8)]Nd-2(4)(mu(4)-O)} has been prepared and characterized by analyses, infrared spectra, single crystal X-ray diffraction, magnetic susceptibility, conductivity and cyclic voltammetry. The mu(4)-O2- anion is in a square planar coordination environment. Electrochemical studies identify the cluster core as a moiety with a delocalized electron system