Nonreciprocal vortex transport in FeSe superconducting thin films

The superconducting diode effect and nonreciprocal transport effects under an applied magnetic field have been observed in various superconductors [1-3]. These effects are unique to systems with low symmetry, requiring the breaking of both inversion and time-reversal symmetries. In this study, we focus on simpler materials, specifically centrosymmetric FeSe thin films. We grew FeSe films with a thickness of 23 nm on a LaAlO₃ substrate by pulsed laser deposition (PLD) and subsequently deposited amorphous Si as a protective capping layer. Through detailed measurements of I-V characteristics under magnetic fields below the transition temperature, while carefully avoiding heating effects, we demonstrate that nonreciprocal resistance arises in these simple structures owing to symmetry breaking at the interfaces. One of the key mechanisms behind these effects is the asymmetric vortex dynamics. Additionally, we investigated the nonreciprocal flux-flow Hall effect of vortices, and its underlying origins will be discussed in the presentation. Our results provide new insights into the control of vortex dynamics in superconductors. [1] R. Wakatsuki et al., Sci. Adv. 3, e1602390 (2017). [2] E. Zhang et al., Nat. Commun. 11, 5634 (2020). [3] M. Masuko et al., npj Quantum Mater. 7, 104 (2022).