CDW STATE AND SUPERCONDUCTIVITY IN THE QUASI-2-DIMENSIONAL MONOPHOSPHATE TUNGSTEN BRONZE P4W14O50

The monophosphate tungsten bronzes (PO2)(4)(WO3)(2m) are quasi two-dim ensional conductors which show electronic instabilities of the Peierls type, The m = 7 member of the series P4W14O50, undergoes two successi ve Peierls transitions at T-P1 = 188 K and T-P2 = 60K. Weak localisati on effects are observed in the low temperature charge density wave sta te, Resistivity, magnetoresistance and a.c. susceptibility measurement s establish that a superconducting transition takes place at temperatu res lower than approximately T-c = 0.3 K. This indicates that supercon ductivity is related to parts of the Fermi surface left over after the Peierls gap openings. (C) 1997 Elsevier Science Ltd.