Catálogo de publicaciones - revistas

<jats:p>The Nb<jats:sub>3</jats:sub>Sn thin film cavity, having the potential to be operated at a higher temperature and higher gradient compared to the cavity made from bulk niobium, is one of the most promising key technologies for the next-generation radio-frequency superconducting accelerators. In our work, several 1.3 GHz single-cell TESLA-shaped Nb<jats:sub>3</jats:sub>Sn thin film cavities, coated by the vapor diffusion method, were tested at Peking University and Institute of Modern Physics, Chinese Academy of Sciences. It was observed that the performance of the Nb<jats:sub>3</jats:sub>Sn thin film cavities in the tests without the slow cooling down procedure and the effective magnetic field shielding was significantly improved by using a low temperature baking at 100 °C for 48 hours. Although the peak electric field of the cavity remained unchanged, the rapid drop of the unloaded <jats:italic>Q</jats:italic> value (<jats:italic>Q</jats:italic> <jats:sub>0</jats:sub>) with the increasing accelerating field (<jats:italic>Q</jats:italic>-slope) was effectively eliminated, resulting in an improvement of the <jats:italic>Q</jats:italic> <jats:sub>0</jats:sub> in the intermediate field region by ∼ 8 times. Furthermore, under better test conditions with the shielded magnetic field less than 5 mG and the slow cooling down procedure in the temperature range of 25–15 K, the <jats:italic>Q</jats:italic> <jats:sub>0</jats:sub> was still improved by about 20%. Our study shows that the low temperature baking can be an effective supplement to the effective post-treatment for the Nb<jats:sub>3</jats:sub>Sn thin film cavity.</jats:p>

<jats:p>Graphene has afforded an ideal 2D platform for investigating a rich and fascinating behavior of Dirac fermions. Here, we develop a theoretical mechanism for manipulating the Dirac fermions in graphene, such as from type-I to type-II and type-III, by a top-down nanopatterning approach. We demonstrate that by selective chemical adsorption to pattern the 2D graphene into coupled 1D armchair chains (ACs), the intrinsic isotropic upright Dirac cone becomes anisotropic and strongly tilted. Based on model analyses and first-principles calculations, we show that both the shape and tilt of Dirac cone can be tuned by the species of chemisorption, e.g., halogen vs hydrogen, which modifies the strength of inter-AC coupling. Furthermore, the topological edge states and transport properties of the engineered Dirac fermions are investigated. Our work sheds lights on understanding the Dirac fermions in a nanopatterned graphene platform, and provides guidance for designing nanostructures with novel functionality.</jats:p>

<jats:p>Thermoelectric performance of InSb is restricted by its low Seebeck coefficient and high thermal conductivity. Here, CuCl is employed to optimize simultaneously the electrical and thermal transport properties of InSb. The substitution of Cl for Sb results in enhanced electron effective mass, leading to high Seebeck coefficient of –159.9 μV/K and high power factor of 31.5 μW⋅cm<jats:sup>−1</jats:sup>⋅K<jats:sup>−2</jats:sup> at 733 K for InSb + 5 wt% CuCl sample. In addition, CuCl doping creates hierarchical architectures composed of Cu<jats:sub>9</jats:sub>In<jats:sub>4</jats:sub>, Sb, Cu<jats:sub>2</jats:sub>Sb in InSb, leading to a strengthened phonon scattering in a wide wavelength (i.e., nano to meso scale), thus a low lattice thermal conductivity of 2.97 W⋅m<jats:sup>−1</jats:sup>⋅K<jats:sup>−1</jats:sup> at 733 K in InSb + 5 wt% CuCl. As a result, a maximum <jats:italic>ZT</jats:italic> of 0.77 at 733 K has been achieved for the InSb + 5 wt% CuCl sample, increasing by ∼ 250% compared to pristine InSb.</jats:p>