Abstract Body

Recently, various phenomena, including superconducting diode effect (SDE), have been observed in noncentrosymmetric superconductors^1,2. Recent experiments have demonstrated the zero-field SDE, wherein the superconducting current flows only in the forward direction, indicating that the proximity effect at the superconductor/ferromagnet interface can be used to effectively control the SDE^3-5. Zero-field SDEs have the potential to enable novel nonvolatile memory devices and logic circuits with ultralow power consumption.

The proximity effect between ferromagnets and superconductors has been actively studied using ferromagnet/superconductor/ferromagnet structures^6-8. In such structures, the superconducting properties can be controlled by the parallel and antiparallel states of magnetization, and the transition temperature of a superconductor sandwiched by a ferromagnet depends on the magnetization state because of the proximity effect^7-9.

In this study, we successfully fabricated noncentrosymmetric superconducting multilayers containing ferromagnets, superconductors, and heavy metals5 with parallel and antiparallel magnetization states, as shown in Figure 1. Magnetic hysteresis that reflects the magnetization state was observed in the nonreciprocal critical current characteristics. When the magnetization directions of the upper and lower ferromagnets that sandwich the superconducting layer are parallel, the nonreciprocal critical current becomes finite. However, it becomes zero when the magnetization directions are antiparallel. This feature enables to control the polarity-reversible and on–off switching of the zero-field SDE.

References

[1] N. Nagaosa, Y. Yanase, Annu. Rev. Condens. Matter Phys. 15, 63 (2024).

[2] F. Ando et al., Nature 584, 373 (2020).

[3] H. Narita et al., Nat. Nanotechnol. 17, 823 (2022).

[4] K.-R. Jeon et al., Nat. Mater. 21, 1008 (2022).

[5] H. Narita et al., Adv. Mater. 35, 2304083 (2023).

[6] A. I. Buzdin, Rev. Mod. Phys. 77, 935 (2005).

[7] Y. Gu et al., Phys. Rev. Lett. 115, 067201 (2015).

[8] Y. Zhu et al., Nat. Mater. 16, 195 (2017).

[9] A. Di Bernardo et al., Nat. Mater. 18, 1194 (2019).

Acknowledgment

This work was partly supported by JSPS KAKENHI (Grant Nos. 21K13883, 21K18145, 24H00007, and 24K00584) and JST PRESTO (Grant No. JPMJPR2358). This study was also supported by the research grant program of the Futaba Foundation, Iketani Science and Technology Foundation, Tokuyama Science Foundation, Iwatani Naoji Foundation, Murata Science and Education Foundation, and Mazda Foundation. We also acknowledge the MEXT Initiative to Establish Next-generation Novel Integrated Circuits Centers (X-NICS) (Grant No. JPJ011438) and the Collaborative Research Program of the Institute for Chemical Research, Kyoto University.