[PC8] Nickelates, Iron-based

3:30 PM - 4:00 PM JST(6:30 AM - 7:00 AM UTC)

[PC8-03-INV] Access to Depairing Regime in Supercurrent Transport of Single-Crystal Nanobridges Made of Iron Based Superconductors

*Haruhisa Kitano¹ (1. Aoyama Gakuin University (Japan))

Keywords:

Depairing current,Focused ion beam,Iron based superconductor

In the practical superconducting devices such as transition-edge sensors (TES) and superconducting nanowire single photon detectors (SNSPD), the performance of the non-equilibrium supercurrent transport is crucially import, rather than the equilibrium properties. As well known, the critical current in a bulk sample is determined by the beginning of vortex flow driven by the Lorentz force. On the other hand, the supercurrent in a narrow strip, fabricated from the superconducting thin films, enables the access to the depairing regime where vortices are expelled from the narrow strip and the Cooper pairs begin to be broken by the increased kinetic energy of superfluid [1]. Many of the superconducting nanowires fabricated from the artificially grown thin films have been devoted to the measurements of the depairing current density, J_d [2]. Here, we present the recent studies using the single-crystal nanobridges of FeTe_1-xSe_x [3,4], BaFe₂(As_1-xP_x)₂ [5,6] and Ba(Fe_1-xCo_x)₂As₂ [7], which were carefully fabricated by using the focused ion beam (FIB) techniques. The magnitude and the temperature- and field dependences of the critical current density J_c strongly suggest that the measured critical current come close to the depairing regime, indicating the advantage to the FIB-based nanobridges. We show that the anisotropy of J_d in FeTe_1-xSe_x is determined by that of the effective mass and that the doping-dependent J_d along the c axis in BaFe₂(As_1-xP_x)₂ and Ba(Fe_1-xCo_x)₂As₂ has a similar dome to that of T_c, in contrast to the doping dependences of l_L and the depinning J_c. We also discuss the I-V characteristics of the nanobridges, indicating the contribution of the non-equilibrium Josephson effect and the phase slips occurring near the depairing limit. All results clearly show that the FIB-based single-crystal nanobridges are quite useful to probe the intrinsic properties near the depairing limit of the non-equilibrium supercurrent. [1] J. Romijn et al., PRB 26, 3648 (1982). [2] V. Rouco et al., Nano Lett. 19, 4174 (2019). [3] Y. Sun et al., PRB 101, 134516 (2020). [4] T. Miyazawa et al., J. Phys.: Conf. Ser. 1975, 012010 (2021). [5] Y. Mizukoshi et al., PRB 110, 104501 (2024). [6] S. Suzuki et al., (submitted to SuST) [7] H. Kitano et al., (in preparation)