2-DIMENSIONAL DECOHERENCE EFFECTS IN SUPERCONDUCTING SHEETS OF SINGLE-CRYSTAL BI2SR2CACU2O8+X

We quantitatively analyze ohmic magnetoresistance of a Bi2Sr2CaCu2O8+x Single crystal in the temperature range 40 K less than or equal to T less than or equal to 76 K and in magnetic fields up to 0.8 T, with an emphasis on the non-Arrhenius high-resistivity data. The unusual fiel d dependence of the magnetoresistance at high resistivities is shown t o follow a behaviour which is characteristic for decoherence effects i n two-dimensional systems. We give semiquantitative arguments which re late the observed behaviour to the magnetic-field-induced breaking of non-dissipative quasiparticle pairs occurring in the mixed state withi n the isolated double CuO2 sheets. These arguments generalize the appr oach to the quantum decoherence phenomena, originally developed for T >T-c to T <T-c. (C) 1997 Elsevier Science B.V.