Fluctuating Fractionalized Spins in Quasi Two-dimensional Magnetic V0.85PS3

TL;DR

This study provides experimental evidence of fractionalized spins in V0.85PS3, revealing a crossover to a spin liquid-like regime at 200 K through Raman spectroscopy, highlighting strong phonon-Majorana fermion coupling.

Contribution

It demonstrates the coupling of phonons with fractionalized Majorana fermions and identifies a crossover temperature indicating proximity to a quantum spin liquid state in V0.85PS3.

Findings

Emergence of low frequency quasielastic response at T* ~ 200 K

Broad magnetic continuum indicating spin fractionalization

Anomalies in phonon self-energy parameters at T*

Abstract

Quantum spin liquid (QSL), a state characterized by exotic low energy fractionalized excitations and statistics is still elusive experimentally and may be gauged via indirect experimental signatures. Remnant of QSL phase may reflect in the spin dynamics as well as quanta of lattice vibrations, i.e., phonons, via the strong coupling of phonons with the underlying fractionalized excitations i.e., Majorana fermions. Inelastic light scattering (Raman) studies on V1-xPS3 single crystals evidences the spin fractionalization into Majorana fermions deep into the paramagnetic phase reflected in the emergence of a low frequency quasielastic response along with a broad magnetic continuum marked by a crossover temperature T* ~ 200 K from a pure paramagnetic state to fractionalized spins regime qualitatively gauged via dynamic Raman susceptibility. We further evidenced anomalies in the phonons self-energy parameters in particular phonon line broadening and line asymmetry evolution at this crossover temperature, attributed to the decaying of phonons into itinerant Majorana fermions. This anomalous scattering response is thus indicative of fluctuating fractionalized spins suggesting a phase proximate to the quantum spin liquid state in this quasi two-dimensional (2D) magnetic system.