C.N. Jiang

An improved analysis of resistivity from flux transformer geometry

Abstract We present two algorithms for the calculation of the resistivity tensor from current/voltage measurements for the two different contact configurations: “flux transformer” and “ I ‖ c ”. The application of this method is illustrated on data for an Y 0.78 Pr 0.22 Ba 2 Cu 3 O 7− δ single crystal.

In-plane and out-of-plane resistivities of PrBa2Cu3O7−δ and Y0.47Pr0.53Ba2Cu3O7−δ single crystals☆

Abstract We report out-of-plane and in-plane normal-state resistivities of twinned, fully-oxygenated single crystals of insulating PrBa2Cu3O7−δ and superconducting Y0.47Pr0.53Ba2Cu3O7−δ (Tc ≈ 18 K) measured by the flux transformer method. In the latter specimen, the onset of superconductivity was suppressed by a magnetic field of 9 T. The anisotropy ϱ c /ϱ ab = a +_bT −2 3 for both samples, increasing monotonically at low temperatures with no sign of saturation. The absence of saturation and the T −2 3 dependence indicate two-dimensional transport. These data also represent a direct observation of hopping conduction in a homogeneous superconductor.

Normal-state out-of-plane and in-plane resistivities of Y1−xPrxBa2Cu3O7−δ (0 < x ≤ 1) single crystals

Abstract Out-of-plane resistivity and anisotropy of fully-oxygenated Y 1− x Pr x Ba 2 Cu 3 O 7− δ (0 x ≤ 1) single crystals demonstrate a unique non-monotonic variation with Pr concentration x. The strongly temperature-dependent anisotropy reaches a maximum at x ≈ 0.4 ( T c ≈ 45 K ), and decreases for both higher and lower T c samples.

Flux motion in underdoped Y1−xPrxBa2Cu3O7−δ single crystals

Abstract Vortex flow in strongly underdoped Y 1− x Pr x Ba 2 Cu 3 O 7−δ single crystals has been studied by the flux transformer technique. Two notable features can be identified: the asymmetric growth of the vortices and their finite residual mobility at low temperatures.

Evolution of c-axis resistivity in Y1−xPrxBa2Cu3O7−δ single crystals

We report on the systematic study of the evolution of the in-plane (ρab) and out-of-plane (ρc) resistivities of fully oxygenatedY1−xPrxBa2Cu3O7−δ single crystals. ρc(x) exhibits a non-monotonic behavior: at low to moderatex, ρc(x) and the anisotropy ρc(x) increase, reaching a maximum at x≈0.42; for higherx,x, ρc and ρc/ρcab decrease, while ρab continues to increase monotonically. These results, along with the coexistence of metallic ρab(T) and semiconducting ρc(T), are consistent with the presence of a gap in the energy spectrum of the chains, leading to tunneling through both valence and conduction bands of theCuO chains.