Structural Evolution from Hyper-Honeycomb to Honeycomb Networks and Superconductivity in LaPtxSi2-x

Abstract

We report the crystal structures and superconductivity (SC) of LaPtxSi2-x (0.5 <= x <= 1.0) that are solid solutions of LaSi2 and LaPtSi with centrosymmetric tetragonal (I41/amd, D 19 4 h , #141) and non-centrosymmetric tetragonal (I41md, C 11 4 v , #109) structures, respectively. It was found that at 0.86 <= x <= 1.00, the non-centrosymmetric tetragonal symmetry is preserved, while partial disorder appears in alternating Pt and Si of the hyper-honeycomb network. The superconducting transition temperature T c was drastically reduced from 3.9 to 1.5 K as x varies from 1.0 to 0.86. Additionally, a hexagonal phase with an AlB2-type structure (P6/mmm, D 16 h , #191) has been discovered at 0.50 <= x <= 0.71 with a honeycomb network of statistically distributed Pt and Si atoms. The hexagonal phase exhibited SC at T c = 0.38 K. This system provides an opportunity to investigate the relationship between topological electronic states, SC, and disorders.