Excitations with fractional spin less than 1/2 in frustrated magnetoelastic chains

TL;DR

This paper demonstrates that in frustrated magnetoelastic chains, single spin-flip excitations on certain plateaux decay into multiple fractionalized excitations with spin 1/N, revealing new fractionalization phenomena beyond known magnon decay.

Contribution

The study uncovers a novel fractionalization of magnetic excitations into fractional spin units in frustrated chains, supported by DMRG computations and analytical theory.

Findings

Single spin-flip decays into N fractional excitations with spin 1/N.

Microscopic structure of domain walls with fractional spin 1/3 elucidated.

Predicted excitations are noninteracting and experimentally observable.

Abstract

We study the magnetic excitations on top of the plateaux states recently discovered in spin-Peierls systems in a magnetic field. We show by means of extensive density matrix renormalization group (DMRG) computations and an analytic approach that one single spin-flip on top of $M=1-\frac2N$ ($N=3,4,...$) plateau decays into $N$ elementary excitations each carrying a fraction $\frac1N$ of the spin. This fractionalization goes beyond the well-known decay of one magnon into two spinons taking place on top of the M=0 plateau. Concentrating on the $\frac13$ plateau (N=3) we unravel the microscopic structure of the domain walls which carry fractional spin-$\frac13$, both from theory and numerics. These excitations are shown to be noninteracting and should be observable in x-ray and nuclear magnetic resonance experiments.