Spinon confinement and a sharp longitudinal mode in Yb<sub>2</sub>Pt<sub>2</sub>Pb in magnetic fields.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30850591.
- Also identified by DOI 10.1038/s41467-019-08715-y and PMC identifier 6408591.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The fundamental excitations in an antiferromagnetic chain of spins-1/2 are spinons, de-confined fractional quasiparticles that when combined in pairs, form a triplet excitation continuum. In an Ising-like spin chain the continuum is gapped and the ground state is Néel ordered. Here, we report high resolution neutron scattering experiments, which reveal how a magnetic field closes this gap and drives the spin chains in Yb<sub>2</sub>Pt<sub>2</sub>Pb to a critical, disordered Luttinger-liquid state. In Yb<sub>2</sub>Pt<sub>2</sub>Pb the effective spins-1/2 describe the dynamics of large, Ising-like Yb magnetic moments, ensuring that the measured excitations are exclusively longitudinal, which we find to be well described by time-dependent density matrix renormalization group calculations. The inter-chain coupling leads to the confinement of spinons, a condensed matter analog of quark confinement in quantum chromodynamics. Insensitive to transverse fluctuations, our measurements show how a gapless, dispersive longitudinal mode arises from confinement and evolves with magnetic order.