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.

Figure 1

(Color online) Dynamical spin structure factor $S\left(q,\omega \right)$ for the MG model at $T/J=0.1$ within the whole range of $q\le \pi$, calculated by the FTD-DMRG method on a system of $N=60$ sites. Correction vector improvement of high $\omega$ part was preformed only for $q\ge 13\pi /15$.

Figure 2

(Color online) $S\left(q=\pi ,\omega \right)$ for different $T/J=0.0$, 0.1, 0.3, and 0.5 where the broadening of central peak with increasing $T$ is well pronounced.

Figure 3

(Color online) $T=0$ dynamical spin structure factor $S_0\left(q=\pi ,\omega \right)$ as calculated via the DMRG for $N=100$ sites (full line), numerically within the two-spinon approximation (dashed line) and using simplified ${\tilde{\zeta }}_q\left(k\right)$ (dotted line).

Figure 4

(Color online) Static susceptibility ${\chi }_q\left(T\right)$ vs $T$ for different $q\le \pi$ for $\alpha =0.5$ as obtained with the FTLM.

Figure 5

(Color online) Local spin correlations $S_L\left(\omega \right)$ for $\alpha =0.5$ and 0.7 at $T=0.1$ and 0.3 as obtained with the FTD-DMRG method.