TRANSPORT-PROPERTIES OF BI2SR2CACU2O8 CRYSTALS WITH AND WITHOUT SURFACE BARRIERS

Bi2Sr2CaCu2O8 crystals with electrical contacts positioned far from th e edges are studied by transport measurements, then cut into narrow st rip geometry, and remeasured. Instead of showing larger resistance, th e strips display a dramatic drop in the resistance, enhanced activatio n energy, and nonlinear behavior due to strong surface barriers. The s urface barriers also dominate the resistive drop at the first-order ph ase transition. Because the surface barriers are avoided in large crys tals, we are able to probe the solid phase and find good agreement wit h the recent predictions of Bragg glass theory. [S0031-9007(98)07485-7 ].