Effect of dimensional crossover on magnetoresistance of YBa 2Cu 3O 7/PrBa 2Cu 3O 7 superlattices

Abstract

We have studied magnetoresistance of the YBa 2Cu 3O 7/PrBa 2Cu 3O 7 (YBCO/PrBCO) superlattices with different thickness of the separator layer (YBCO/PrBCO = 1:1, 1:3 and 1:5) in fields up to 12T at T < T c. An excellent fitting by the Larkin two-dimensional superconducting fluctuation theory with only two scaling parameters (A(T) and H Φ(T)) for each R(T) curve shows that it is possible to apply this approach to interpret our magnetoresistance data. The resistive transition broadening in a magnetic field can be related to giant conductivity fluctuations in the quasi two-dimensional double CuO 2 superconducting layers in YBCO. The magnetoresistance increases with further separation of YBCO in the superlattices with a larger thickness of the PrBCO separator layers. For YBCO/PBCO = 1:3 and 1:5 superlattices, the first scaling parameter A(T) determined by the fluctuation amplitude follows quite well the Larkin β(T) function typical for 2D systems. For YBCO/PrBCO = 1:1, the YBCO layers are not completely decoupled and A(T) deviates from β(T). The temperature dependence of the second scaling parameter H Φ(T), the phase coherence breaking field, is consistent with the theoretical prediction by Reizer for the quasi-two-dimensional electron-electron interactions.