Superconductivity in BaTi₂Sb₂O with a<i>d</i>¹Square Lattice

Abstract

We prepared a new two-dimensional oxyantimonide, BaTi 2 Sb 2 O, which shows a superconducting transition at 1.2 K, representing the first superconductivity in a system with Ti 3+ ( d 1 ) in a square lattice. The TiO 2 Sb 4 mixed anionic coordination stabilizes a unique half-filled Ti d x y orbital configuration in Ti 2 O plane, which is analogous to Cu 2+ ( d 9 ) in the high- T c superconductors. A charge density wave (CDW)- or spin density wave (SDW)-like anomaly appears at 50 K, which is significantly reduced compared with 200 K for the isostructural and non-superconducting BaTi 2 As 2 O.