We measured the complex conductivity of single crystals of Eu2CuO4 from 3 to 15 GHz and observed collective transport with a sample-independent spectral weight. An unusual activated temperature dependence for the spectral weight, and anomalous temperature dependence of the Eu Mossbauer line, indicate magnetic effects well above the Néel temperature. The collective transport is similar to that observed in (TMTSF)2PF6 where TMSF denotes tetramethyltetrathiofulvalene and where charged, massive solitons are the suspected source of the transport. © 1988 The American Physical Society.

Static and microwave measurements of the electronic response of the planar cuprate Eu2CuO4 provide evidence for thermally activated collective excitations. These observations together with microwave and other measurements on superconductors suggest that paired charge-carrying objects may exist both above and below Tc in the superconductors. If these objects, which can be related to solitons of a spin density wave ground state, play a role in superconductivity, certain conclusions may be drawn. We discuss here the evidence for such objects and their implications. © 1989.