SUPERCONDUCTIVITY ABOVE 130-K IN THE HG-BA-CA-CU-O SYSTEM

THE recent discovery1 of superconductivity below a transition temperat ure (T(c)) of 94 K in HgBa2CuO4+delta has extended the repertoire of h igh-T(c) superconductors containing copper oxide planes embedded in su itably structured (layered) materials. Previous experience with simila r compounds containing bismuth and thallium instead of mercury suggest ed that even higher transition temperatures might be achieved in mercu ry-based compounds with more than one CuO2 layer per unit cell. Here w e provide support for this conjecture, with the discovery of supercond uctivity above 130 K in a material containing HgBa2Ca2Cu3O1+x (with th ree CuO2 layers per unit cell), HgBa2CaCu2O6+x (with two CuO2 layers) and an ordered superstructure comprising a defined sequence of the uni t cells of these phases. Both magnetic and resistivity measurements co nfirm a maximum transition temperature of approximately 133 K, distinc tly higher than the previous established record value of 125-127 K obs erved in Tl2Ba2Ca2Cu3O10 (refs 2, 3).