Non-equilibrium Muon Dynamics Imitating Fractional Spin Excitations in a Quantum Spin Chain
Year: 2026
Type: preprint
Abstract: Fractional spin excitations in low-dimensional and frustrated magnets are commonly associated with sporadic spin fluctuations, as observed in quantum spin liquids, spin ices, and other complex magnetic states. In this study, we investigate the spin dynamics in the amplitude-modulated magnetic ground state of AgCuVO$_4$, a spin-1/2 chain compound with competing intrachain interactions, by muon spectroscopy. Our data reveal a Gaussian decay of muon polarization that remains remarkably resilient against applied magnetic fields---a behavior often interpreted as evidence of emergent sporadic spin dynamics. However, density functional theory calculations of muon stopping sites and their quadrupolar level-crossing resonance spectra suggest an alternative mechanism: a two-state model where the muon randomly hops between two nearby sites, eventually equilibrating across both on a microsecond timescale via quantum delocalization. These findings provide a microscopic explanation for the field-resilient muon polarization and indicate that such behavior may not always stem from intrinsic spin fluctuations, but can also arise from non-equilibrium muon dynamics.
Source: arXiv (Cornell University)
Language: English
Subfield: Condensed Matter Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: Evolution of the complex magnetic and polar orders from simple 2D scaffolds in the layered hybrid organic-inorganic halometallates, G2322983178, Controllable broadband electromagnetic-radiation shielding, Quantum effects of light particles in materials, Physics of quantum and functional materials, G5227424747, Practical quantum advantage of reservoir computing on NISQ devices, G56540651, Anisotropic quantum magnetism in novel rare-earth materials, G6294822029, Entangled and delocalized states of muons and nuclei, G6737868193, G7671417569
OpenAlex ID: W7222501865