Entanglement between a muon spin and $I>\frac{1}{2}$ nuclear spins

TL;DR

This paper demonstrates quantum entanglement between muon spins and quadrupolar nuclear spins in vanadium compounds, showing muons as sensitive probes for local structural and electronic environments in materials.

Contribution

First observation of quantum coherence between muon and quadrupolar nuclear spins, expanding muon applications to structural and charge sensing in materials.

Findings

Entanglement observed in vanadium intermetallics with A15 structure

Muons can probe local structural and electronic environments

Potential for muons as quantum sensors in materials science

Abstract

We report on the first example of quantum coherence between the spins of muons and quadrupolar nuclei. We observe this effect in vanadium intermetallic compounds which adopt the A15 crystal structure, and whose members include all technologically dominant superconductors. The entangled states are extremely sensitive to the local structural and electronic environments through the electric field gradient at the quadrupolar nuclei. This case-study demonstrates that positive muons can be used as a quantum sensing tool to probe also structural and charge related phenomena in materials, even in the absence of magnetic order.