Enhanced Superconductivity in Close Proximity to Polar-Nonpolar Structural Phase Transition in Se/Te-Substituted PtBi2

The novel CdI2-type compounds Pt(Bi(1-x)Ch(x))(2) (Ch = Se, Te) were synthesized. Powder X-ray diffraction experiments and Rietveld analysis revealed that the partial substitution of Ch for Bi induces a structural phase transition from the noncentrosymmetric polar structure of trigonal PtBi2 (P31m, C-3v(2), No. 157) to the centrosymmetric nonpolar CdI2-type structure (P (3) over bar m1, D-3d(3), No. 164), which consists of stacked Pt(Bi(1-x)Ch(x))(2) layers formed by edge-sharing PtBi6 octahedra. Magnetization, electrical resistivity, and specific heat measurements confirmed the emergence of superconductivity at the transition temperature T-c = 1.9-2.4 and 2.0-2.4 K in Pt(Bi1-xSex)(2) and Pt(Bi1-xTex)(2), respectively. These temperatures are much higher than T-c = 0.6 K of trigonal PtBi2. The superconducting phases lie in the vicinity of the polar-nonpolar structural phase boundary.

Automated summary

Novel CdI2-type compounds Pt(Bi(1-x)Ch(x))(2) (Ch = Se, Te) were synthesized, and it was found that the partial substitution of Ch for Bi induces a structural phase transition. The layered structure of Pt(Bi(1-x)Ch(x))(2) is formed by edge-sharing PtBi6 octahedra. Magnetization, electrical resistivity, and specific heat measurements confirmed the emergence of superconductivity at higher temperatures in Pt(Bi1-xSex)(2) and Pt(Bi1-xTex)(2), which are located near the polar-nonpolar structural phase boundary.