Muon diffusion and trapping studies in high purity vanadium

We present the first results of a study of the effects of varying impurity concentration on the temperature dependence of the depolarization rate of positive muons implanted into vanadium. Data are reported for the most highly purified polycrystalline sample yet measured, and the same sample subsequently doped with about 500 ppm oxygen by weight. The data for the pure sample shows a low depolarization rate (<.15 sec^–1) at all temperatures measured, showing a broad minimum centered at 35 K, followed by a sharp peak near 90 K and a rapid drop to negligible values at 200 K. The data is contrasted with previously published data [2] on less pure samples, and calls into question previous interpretations of the behavior of the ⁺ at low temperatures in impure vanadium [1] as one-phonon-assisted tunneling.This work was supported by the U. S. Department of Energy     

Coexisting holes and electrons in high-T C materials: implications from normal state transport

Normal state resistivity and Hall effect are shown to be successfully modeled by a two-band model of holes and electrons that is applied self-consistently to (i) dc transport data reported for eight bulk-crystal and six oriented-film specimens of YBa₂Cu₃O_7?δ, and (ii) far-infrared Hall angle data reported for YBa₂Cu₃O_7?δ and Bi₂Sr₂CaCu₂O_8+δ. The electron band exhibits extremely strong scattering; the extrapolated dc residual resistivity of the electronic component is shown to be consistent with the previously observed excess thermal conductivity and excess electrodynamic conductivity at low temperature. Two-band hole–electron analysis of Hall angle data suggests that the electrons possess the greater effective mass.