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Anharmonic quantum effects of implanted muons: Route to probing nuclear quantum behavior in solids

F. Hotz1,*, M. Gomilšek2,3,†, T. Arh1, T. J. Hicken1, P. Umek2, A. Zorko2,3, and H. Luetkens1

  • 1PSI Center for Neutron and Muon Sciences CNM, CH-5232 Villigen PSI, Switzerland
  • 2Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana, Slovenia
  • 3Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, SI-1000 Ljubljana, Slovenia

  • *Contact author: fabian.hotz@psi.ch
  • †Contact author: matjaz.gomilsek@ijs.si
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Phys. Rev. B 113, 224420 – Published 8 June, 2026

DOI: https://doi.org/10.1103/x1y3-9chs

Abstract

The quantum behavior of light particles in solids gives rise to phenomena that cannot be captured by a classical description. We show that muon spin spectroscopy (μSR), when paired with a quantum-mechanical treatment of the implanted muon, becomes a sensitive and direct probe of nuclear quantum effects. By modeling the muon as a spatially extended quantum particle, our approach captures strong anharmonic behavior. We demonstrate this in Zn-barlowite, which serves as a nontrivial test case due to its structurally complex lattice and the presence of both fluorine and hydroxyl groups. Our results establish a route for extracting nuclear quantum signatures from μSR data and open different opportunities for studying light nuclei such as hydrogen and lithium in systems where quantum fluctuations shape structure and function.

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Phys. Rev. B 113, 224420– Published 8 June, 2026
  • Received 17 July 2025
  • Revised 18 March 2026
  • Accepted 7 April 2026
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