Evidence for an Incommensurate High-Field Phase in the Spin-Peierls System Tetrathiafulvalene-AuS4C4(CF3)4

Abstract

Frequency-dependent proton and fluorine NMR experiments have been performed on tetrathiafulvalene-Au${\mathrm{S}}_4$ ${\mathrm{C}}_4$ ${\left(\mathrm{C}{\mathrm{F}}_3\right)}_4$, which give the first experimental evidence for the incommensurate nature of the high-field phase in spin-Peierls systems. The field-induced transition to this phase is found to be first order at low temperatures. The echo shape in the high-field phase is described in terms of a soliton-lattice model due to Nakano and Fukuyama.