Measuring Superconducting Stiffness and Coherence of Magnetic Materials with zero-applied field

  Amotz Peri  ,  Avior Almoalem  ,  Amit Kanigel  ,  Amit Keren  
Dept. of Physics, Technion Israel Institute of Technology, Haifa, Israel

Superconducting (SC) stiffness ρs and coherence length ξ are usually measured by applying a magnetic field and measuring its penetration depth into a material λ, and the upper critical field Hc2. However, in magnetic materials, e.g. iron-based superconductors, this could lead to erroneous results since the field couples to the magnetic moments. To overcome this problem, we applied the Stiffnessometer technique1 to measure both quantities in FeSeTe. In this technique one applies rotor-free vector potential A to a SC ring and measures with a SQUID the current density J via its magnetic moment M of the SC. ρs, and ξ are determined from London’s equation J=−ρsA and its range of validity as in Fig. 1. Our results will be compared with theoretical expectations and other techniques

Fig. 1: Magnetic moment of a ring-shaped FeSeTe superconductor as a result of current in an excitation coil, Iec, which pierces the ring. In this configuration the ring does not experiences a magnetic field.



[1]. I. Mangel, I. Kapon, N. Blau, K. Golubkov, N. Gavish, and A. Keren, Phys. Rev. B 102, 024502 (2020).