New superconductor SrPt2Ge2 with Tc=10.2K

• DOI: 10.1016/j.physc.2013.03.036
• Publication Date: 2013-04-08T07:46:40Z
• Authors: H.C. Ku; I.A. Chen; C.H. Huang; C.W. Chen; Y.B. You; M.F. Tai; Y.Y. Hsu
• Keywords: 0103 physical sciences; 01 natural sciences

Abstract Contrast to superconducting compounds SrNi 2 Ge 2 ( T c = 1.1 K) and SrPd 2 Ge 2 ( T c = 3.2 K) with the BaFe 2 As 2 -type body-center-tetragonal (122-bct) layer structure (space group I4/mmm ), SrPt 2 Ge 2 crystallized in a pseudo-tetragonal, monoclinic structure with space group P2 1 and lattice parameters a = 0.4401(4) nm b = 0.4435(4) nm, c = 0.9764(10) nm and β = 90.5 o > 90 o . Superconductivity with T c = 10.2 K was observed in this new compound. However, a weak diamagnetic shielding signal of −3.2 × 10 −2 cm 3 /mol at 2 K indicates that superconductivity is not from the bulk monoclinic phase but from a minor metastable 122-bct high-temperature phase with a ∼ 0.44 nm, c ∼ 0.98 nm, β = 90 o . This is the highest T c reported outside the iron-based layer compounds with the 122-bct structure. High- T c superconductivity is due to strong quasi-2D Pt-Ge-Pt 5 d xz , yz -4 p -5 d xz , yz hybridization in the Pt-Ge layer with squeezed PtGe 4 tetrahedral crystal field and Pt-5 d 8 spin–orbital interaction in the metastable 122-bct phase and is another example of multi-band ( d xz / d yz / d xy ) non-conventional s -wave superconductor.