In-plane current-voltage characteristics and oscillatory Josephson-vortex flow resistance in La-free Bi2+xSr2−xCuO6+δ single crystals in high magnetic fields

Abstract

We have investigated the in-plane I−V characteristics and the Josephson-vortex flow resistance in high-quality La-free Bi2+xSr2−xCuO6+δ (Bi-2201) single crystals in parallel and tilted magnetic fields at temperatures down to 40 mK. For parallel magnetic fields below the resistive upper critical field Hc2∗, the I−V characteristics obey a power law with a smooth change with increasing magnetic field of the exponent from above 5 down to 1. In contrast to the double-layer cuprate Bi-2212, the observed smooth change suggests that there is no change in the mechanism of dissipation (no Kosterlitz-Thouless transition) over the range of temperatures investigated. At small angles between the applied field and the ab plane, prominent current steps in the I−V characteristics and periodic oscillations of Josephson-vortex flow resistance are observed. While the current steps are periodic in the voltage at constant fields, the voltage position of the steps, together with the flux-flow voltage, increases nonlinearly with magnetic field. The ab-flow resistance oscillates as a function of field with a constant period over a wide range of magnetic fields and temperatures. The current steps in the I−V characteristics and the flow resistance oscillations can be linked to the motion of Josephson vortices across layers.

Source-reported materials — not catalogue approval

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