Negligible oxygen vacancies, low critical current density, electric‐field modulation, in‐plane anisotropic and high‐field transport of a superconducting Nd 0.8 Sr 0.2 NiO ₂ /SrTiO ₃ heterostructure

The emerging Ni‐based superconducting oxide thin films are rather intriguing to the entire condensed matter physics. Here, we report some brief experimental results on transport measurements for a 14‐nm‐thick superconducting Nd 0.8 Sr 0.2 NiO 2 /SrTiO 3 thin‐film heterostructure with an onset transition temperature of ~ 9.5 K. Photoluminescence measurements reveal that there is negligible oxygen vacancy creation in the SrTiO 3 substrate during thin‐film deposition and post chemical reduction for the Nd 0.8 Sr 0.2 NiO 2 /SrTiO 3 heterostructure. It was found that the critical current density of the Nd 0.8 Sr 0.2 NiO 2 /SrTiO 3 thin‐film heterostructure is relatively small, ~ 4 × 10 3 A·cm −2 . Although the surface steps of SrTiO 3 substrates lead to an anisotropy for in‐plane resistivity, the superconducting transition temperatures are almost the same. The out‐of‐plane magnetotransport measurements yield an upper critical field of ~ 11.4 T and an estimated in‐plane Ginzburg–Landau coherence length of ~ 5.4 nm. High‐field magnetotransport measurements up to 50 T reveal anisotropic critical fields at 1.8 K for three different measurement geometries and a complicated Hall effect. An electric field applied via the SrTiO 3 substrate slightly varies the superconducting transition temperature. These experimental results could be useful for this rapidly developing field.