Dynamical central peak and spinon deconfinement in frustrated spin chains

Studying the dynamical spin structure factor in frustrated spin chains with spontaneously dimerized ground state we show that besides the gapped spin-wave excitations there appears at finite temperatures also a sharp central peak. The latter can be attributed to deconfined spinons, accounted well within the variational approach. The central peak remains well pronounced within the local spin dynamics and may be relevant for experiments on materials with one-dimensional frustrated spin chains.