title: Tuning of superconducting niobium nitride terahertz metamaterials.
abstract: Superconducting planar terahertz (THz) metamaterials (MMs), with unit cells of different sizes, are fabricated on 200 nm-thick niobium nitride (NbN) films deposited on MgO substrates. They are characterized using THz time domain spectroscopy over a temperature range from 8.1 K to 300 K, crossing the critical temperature of NbN films. As the gap frequency (f(g) = 2Δ0/h, where Δ0 is the energy gap at 0 K and h is the Plank constant) of NbN is 1.18 THz, the experimentally observed THz spectra span a frequency range from below f(g) to above it. We have found that, as the resonance frequency approaches f(g), the relative tuning range of MMs is quite wide (30%). We attribute this observation to the large change of kinetic inductance of superconducting film.
authors.affiliation: Research Institute of Superconductor Electronics, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China.
authors.forename: Jingbo
authors.initials: J
authors.lastname: Wu
authors.forename: Biaobing
authors.initials: B
authors.lastname: Jin
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Xue
authors.forename: Caihong
authors.initials: C
authors.lastname: Zhang
authors.forename: Hao
authors.initials: H
authors.lastname: Dai
authors.forename: Labao
authors.initials: L
authors.lastname: Zhang
authors.forename: Chunhai
authors.initials: C
authors.lastname: Cao
authors.forename: Lin
authors.initials: L
authors.lastname: Kang
authors.forename: Weiwei
authors.initials: W
authors.lastname: Xu
authors.forename: Jian
authors.initials: J
authors.lastname: Chen
authors.forename: Peiheng
authors.initials: P
authors.lastname: Wu
mesh_terms: D003080:Cold Temperature; D004553:Electric Conductivity; D008420:Manufactured Materials; D008422:Materials Testing / Q000379:methods*; D008962:Models, Theoretical; D009556:Niobium / Q000737:chemistry*; D013499:Surface Properties; D055053:Terahertz Radiation
chemical_list: D009556:Niobium