Anharmonic quantum muon effects of light particles in a spin liquid material

TL;DR

This paper demonstrates that modeling muons as quantum particles with anharmonic effects is essential for interpreting muon spin spectroscopy data in quantum spin liquids, revealing the significant influence of light particles on material properties.

Contribution

It introduces a quantum anharmonic modeling approach for muons in materials, improving the understanding of light particle effects in condensed matter systems.

Findings

Classical DFT fails to capture muon quantum effects.

Quantum modeling aligns with experimental $mbda$SR data.

Highlights importance of light particles in material behavior.

Abstract

The quantum behavior of light nuclei and other particles in materials challenges classical intuition and introduces novel phenomena. Here we demonstrate that muon spin spectroscopy ( $\mu$SR) is a powerful tool for exploring the quantum effects of light particles, such as the muon, in condensed matter. The muon's quantum nature is profoundly influenced by the surrounding, offering a unique probe for understanding the role of light atoms and their role in shaping local electronic environments. In Zn-barlowite, a candidate quantum spin liquid, we show that standard density functional theory (DFT) methods, which treat the muon as a classical point-like particle, fail to capture its strong quantum anharmonic effects. Only by modeling the muon as a spatially extended quantum particle, thus accounting for the anharmonicity, can the experimental $\mu$SR data be understood. This approach not only improves the interpretation of $\mu$SR results but also opens the door to studying the quantum effects of other light particles, like hydrogen and lithium nuclei, which can greatly influence material properties.