Hall effect in an untwinned single crystal of YBa2Cu3O7-x

Abstract

The Hall coefficient RH for untwinned single-crystal YBa2Cu3O7-x has been measured for the first time. The crystal was produced by a technique not requiring the application of stress. The measurements are made above the superconducting transition temperature Tc. Near Tc, the conductivity and Hall coefficient RH deviate from their normal-state low-temperature dependences because of fluctuations of small regions of the sample into the superconducting state. These deviations are analyzed to test our present understanding of the dimensionality and superconducting order parameter. We obtain evidence that the two copper-oxide planes in each unit cell are tightly coupled, acting as one superconducting layer. © 1991.