Ir-Sb Binary System: Unveiling Nodeless Unconventional Superconductivity Proximate to Honeycomb-Vacancy Ordering

• DOI: 10.48550/arxiv.2402.06796
• Publication Date: 2024-02-09
• Authors: V. Sazgari; Tianping Ying; J. N. Graham; C. Mielke; Debarchan Das; S. S. Islam; M. Bartkowiak; R. Khasanov; H. Luetkens; Hideo Hosono; Zurab Guguchia
• Keywords: Honeycomb

Vacancies play a crucial role in solid-state physics, but their impact on materials with strong electron-electron correlations has been underexplored. A recent study the Ir-Sb binary system, Ir$_{16}$Sb$_{18}$ revealed novel extended buckled-honeycomb vacancy (BHV) order. Superconductivity is induced by suppressing BHV ordering through high-pressure growth excess Ir atoms or isovalent Rh substitution, although nature of superconducting pairing remained unexplored. Here, we conduct muon spin rotation experiments probing temperature-dependence effective magnetic penetration depth $\lambda_{eff}\left(T\right)$ Ir$_{1-{\delta}}$Sb (synthesized at 5.5 GPa $T_{\rm c}$ = 4.2 K) and ambient pressure synthesized optimally Rh-doped Ir$_{1-x}$Rh$_{x}$Sb ($x$=0.3, 2.7 K). The exponential temperature dependence superfluid density $n_{\rm s}$/m$^{*}$ low temperatures indicates fully gapped state both samples. Notably, ratio to comparable previously measured unconventional superconductors. significant increase sample correlates c}$, hallmark feature superconductivity. We further demonstrate similar effect chemical (Rh substitution) hydrostatic Ir$_{1-x}$Rh$_{x}$Sb, highlighting that dome-shaped phase diagram fundamental material. These findings underscore observed superconductivity, classifies IrSb as first parent ordered vacancies.