In-plane current-voltage characteristics and oscillatory Josephson-vortex flow resistance in La-free Bi$_{2+x}$Sr$_{2-x}$CuO$_{6+\delta}$ single crystals in high magnetic fields

TL;DR

This study investigates in-plane current-voltage behavior and Josephson vortex flow resistance in La-free Bi2201 single crystals under high magnetic fields, revealing smooth dissipation mechanisms and vortex dynamics through oscillatory resistance and current steps.

Contribution

It provides new insights into vortex dynamics and dissipation mechanisms in Bi2201, showing no Kosterlitz-Thouless transition and characterizing vortex flow resistance oscillations.

Findings

Power-law I(V) characteristics with exponent change from >5 to 1

Absence of Kosterlitz-Thouless transition in Bi2201

Oscillatory Josephson-vortex flow resistance with constant period

Abstract

We have investigated the in-plane $I(V)$ characteristics and the Josephson vortex flow resistance in high-quality La-free Bi$_{2+x}$Sr$_{2-x}$CuO$_{6+\delta}$ (Bi2201) single crystals in parallel and tilted magnetic fields at temperatures down to 40 mK. For parallel magnetic fields below the resistive upper critical field $H^{*}_{c2}$, the $I(V)$ characteristic 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 Bi2212, 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.