Quasi-one-dimensional diffusive motion of spin solitons in the spin-Peierls state of (DMe-DCNQI)2Li

(DMe-DCNQI)2Li is a ((1)/(4)) filled spin-Peierls (SP) system with the SP transition temperature Tsp∼65 K. Using frequency variable ESR at temperatures enough below Tsp, the existence of spin solitons which could arise from domains with finite chain length, is demonstrated. It is also found that Tsp is enhanced by hydrostatic pressure and can be reproduced well with Cross-Fisher's relation. Within our knowledge, this is the first example of such good consistency with theory in pressure dependence of Tsp. This is probably due to a high one dimensionality of the electronic structure in (DMe-DCNQI)2Li, even under high pressures