Structural Evolution from Hyper-Honeycomb to Honeycomb Networks and Superconductivity in LaPt$_x$Si$_{2-x}$

TL;DR

This study explores how structural evolution from hyper-honeycomb to honeycomb networks in LaPt$_x$Si$_{2-x}$ affects superconductivity, revealing new phases and the interplay between topology, disorder, and superconductivity.

Contribution

It reports the discovery of new structural phases and their superconducting properties in LaPt$_x$Si$_{2-x}$, highlighting the relationship between crystal symmetry, disorder, and superconductivity.

Findings

Superconductivity observed with $T_c$ up to 3.9 K in certain phases.

Identification of a hexagonal honeycomb phase with $T_c$ = 0.38 K.

Structural transition from hyper-honeycomb to honeycomb networks with varying $x$.

Abstract

We report the crystal structures and superconductivity (SC) of LaPt$_{x}$Si$_{2-x}$ ($0.5 \leq x \leq 1.0$) that are solid solutions of LaSi$_{2}$ and LaPtSi with centrosymmetric tetragonal ($I4_{1}/amd$, $D_{4h}^{19}$, \#141) and non-centrosymmetric tetragonal ($I4_{1}md$, $C_{4v}^{11}$, \#109) structures, respectively. It was found that at $0.86 \leq x \leq 1.00$, 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 $T_{\rm c}$ was drastically reduced from 3.9 K to 1.5 K as $x$ varies from 1.0 to 0.86. Additionally, a hexagonal phase with an AlB$_{2}$-type structure ($P6/mmm$, $D_{6h}^{1}$, \#191) has been discovered at $0.50 \leq x \leq 0.71$ with a honeycomb network of statistically distributed Pt and Si atoms. The hexagonal phase exhibited SC at $T_{\rm c} = 0.38$ K. This system provides an opportunity to investigate the relationship between topological electronic states, SC, and disorders