Spin-Lattice Relaxation via Phasons in a Multisoliton Lattice

The change in the phason spectrum on going from the "incommensurate plane wave" to the "multisoliton lattice" modulation limit has been observed via phason-induced ${}_{}{}^{87}{}_{}{}^{}\mathrm{Rb}$ spin-lattice relaxation in the incommensurate phase of ${\mathrm{Rb}}_2$ ${\mathrm{ZnCl}}_4$. The observed temperature dependence of ${T_1}^{-1\mathrm{}}$ close to the "lock-in" transition reflects the temperature dependence of the "acousticlike" branch of the phason spectrum in a multisoliton lattice.