arXiv subjects

Dan T. Fuchs

Publications and source records attributed to Dan T. Fuchs.

3 recordsLinked to original sources

arXiv1998

Transport properties of BSCCO crystals with and without surface barriers

Large BSCCO crystals with electrical contacts positioned far from the edges are studied by transport measurements, then cut into the common narrow strip geometry, and remeasured. Instead of showing larger resistance, the narrow strip samples display a dramatic drop in the resistance, enhanced activation energies, and nonlinear characteristics due to strong surface barriers. The surface barriers also dominate the resistive drop at the first-order phase transition. Because the surface barriers are avoided in large crystals, we are able to probe the solid phase and find good agreement with the recent predictions of Bragg glass theory.

cond-mat.supr-con↗

arXiv1998

Possible new vortex matter phases in BSCCO

The vortex matter phase diagram of BSCCO crystals is analyzed by investigating vortex penetration through the surface barrier in the presence of a transport current. The strength of the effective surface barrier, its nonlinearity, and asymmetry are used to identify a possible new ordered phase above the first-order transition. This technique also allows sensitive determination of the depinning temperature. The solid phase below the first-order transition is apparently subdivided into two phases by a vertical line extending from the multicritical point.

cond-mat.supr-con↗

arXiv1997

Where does the transport current flow in Bi2Sr2CaCu2O8 crystals?

A new measurement technique for investigation of vortex dynamics is introduced. The distribution of the transport current across a crystal is derived by a sensitive measurement of the self-induced magnetic field of the transport current. We are able to clearly mark where the flow of the transport current is characterized by bulk pinning, surface barrier, or a uniform current distribution. One of the novel results is that in BSCCO crystals most of the vortex liquid phase is affected by surface barriers resulting in a thermally activated apparent resistivity. As a result the standard transport measurements in BSCCO do not probe the dynamics of vortices in the bulk, but rather measure surface barrier properties.

cond-mat.supr-con↗