Mobile Bipolaron In Quasi-1-D Conductor Vanadium Bronzes

The existence of the characteristic bound state of BIPOLARON (a dimerized electron pair of up and down spins on the near neighbour sites) was established by NMR and X ray diffraction measurements in the quasi-1-d conductor MxV205(M= Na,Ag,Li,Cu, and Pb). On the basis of the results of EPR and NMR relaxation, the observed high electrical conductivity along the 1-d axis is interpreted as the COLLECTIVE MOTION of BIPOLARONS. These characteristic properties are discussed with the strong electron-phonon interaction of the rather well localized small polarons in the 3d vanadium bronzes, which is different from the 4d. molybdenum bronzes.