Superconducting properties of hyperbolic metamaterials based on ultrathin layers of NbTiN

Application of the metamaterial dielectric function engineering is capable of enhancing superconducting properties in type I superconductors such as aluminum and tin, leading to tripling of the critical temperature T_c in Al-Al₂O₃ epsilon near zero (ENZ) core-shell metamaterial superconductors. Similar effects have been observed in hyperbolic (superconductor/dielectric) metamaterials [1]. Here, we report on study of effects of metamaterial dielectric function engineering on superconducting properties of ultrathin layers of NbTiN. NbTiN/AlN multilayers with varied number of layers and layer thicknesses were fabricated. Dielectric constants of these metamaterials measured via polarization reflectometry will be reported. Correlation of the results of the transport measurements and the hyperbolic properties of the multilayers will be discussed.
[1] Vera N. Smolyaninova, et al., Sci. Rep. 6, 34140