Frustrated vacancy ordering creates novel quantum properties in Kutinaite, $\mathrm{Ag}_{6}\mathrm{Cu}_{14.4}\mathrm{As}_7$

TL;DR

This study reveals that frustrated vacancy ordering in Kutinaite induces unique quantum properties, challenging traditional views on vacancies and highlighting their potential role in emergent electronic behaviors.

Contribution

It demonstrates how correlated vacancy disorder in Kutinaite leads to novel quantum phenomena, combining experimental and computational methods to uncover this relationship.

Findings

Unprecedented metallic diamagnetism in Kutinaite

Subtle frustrated vacancy ordering of Cu sublattice below 300 K

Vacancy frustration leads to unique quantum properties

Abstract

Ideal crystals are fully ordered, but real-world crystals always contain defects breaking translational symmetry. Random defects in crystals have important implications and they e.g. provide the foundation for semiconductor-based electronic devices. Structurally correlated defects introduce an additional level of complexity, which may lead to novel materials properties, but rationalization of relations between correlated disorder and the emergent material properties are very rare. Here we report that the defect structure of the mineral Kutinaite, Ag6Cu14.4As7, exhibits unprecedented metallic diamagnetism, a hallmark of non-trivial electronic states that require delicate symmetrical protection. Using a combination of X-ray scattering methodologies, simulations, and physical property measurements, we deduced and verified subtle frustrated vacancy ordering of the Cu sublattice when cooling crystals below ~300 K. The vacancy frustration in Kutinaite leads to unique quantum properties, and our study calls for a reconsideration of the role of vacancies as quasi-chemical species in crystals.