Isothermal I–V Curves Reconstruction in Superconducting Single Crystals by Means of Nonlinear AC Transport Experiments

In this work we propose a procedure to obtain the voltage vs current (I-V ) curves by means of AC transport measurements, of particular interest for single crystals mounted on settings in which its thermal coupling to the environment is week, and Joule dissipation can cause unwanted thermal decoupling from the thermometer. We present a simple model that accounts for the overheating of a sample in this type of experimental setup and propose two experimental protocols in which thermal oscillations and gradients on the measured region of the sample can be neglected and the overall temperature shifts can be accounted for and corrected. As an example, we present preliminary results obtained using one of these protocols in a Ba(Fe _0.81 Co _0.09 ) ₂ As ₂ single crystal, mounted on a strain- cell, demonstrating that we are able to obtain reliable I-V curves in the vicinity of a vortex-glass transition that exhibit the expected critical behavior. Both the model and the proposed procedure can be used in a broad spectrum of experimental situations far away the presented example.