Superconductivity from buckled-honeycomb-vacancy ordering

TL;DR

This study uncovers a novel buckled-honeycomb-vacancy ordering in Ir$_{16}$Sb$_{18}$ that influences superconductivity, revealing how vacancy arrangements can induce and suppress superconducting phases in correlated materials.

Contribution

It reports the discovery of a unique vacancy ordering in Ir$_{16}$Sb$_{18}$ and elucidates its role in the emergence and suppression of superconductivity, introducing the concept of correlated vacancies.

Findings

Superconductivity emerges when BHV ordering is suppressed.

BHV ordering originates from vacancy formation energy and Fermi surface nesting.

BHV ordering breaks inversion symmetry and affects electronic density of states.

Abstract

Vacancies are prevalent and versatile in solid-state physics and materials science. The role of vacancies in strongly correlated materials, however, remains uncultivated until now. Here, we report the discovery of an unprecedented vacancy state forming an extended buckled-honeycomb-vacancy (BHV) ordering in Ir$_{16}$Sb$_{18}$. Superconductivity emerges by suppressing the BHV ordering through squeezing of extra Ir atoms into the vacancies or isovalent Rh substitution. The phase diagram on vacancy ordering reveals the superconductivity competes with the BHV ordering. Further theoretical calculations suggest that this ordering originates from a synergistic effect of the vacancy formation energy and Fermi surface nesting with a wave vector of (1/3, 1/3, 0). The buckled structure breaks the crystal inversion symmetry and can mostly suppress the density of states near the Fermi level. The peculiarities of BHV ordering highlight the importance of "correlated vacancies" and may serve as a paradigm for exploring other non-trivial excitations and quantum criticality.