Emergent ferromagnetism with superconductivity in Fe(Te,Se) van der Waals Josephson junctions

Gang Qiu; Hung-Yu Yang; Lunhui Hu; Huairuo Zhang; Chih-Yen Chen; Yanfeng Lyu; Christopher Eckberg; Peng Deng; Sergiy Krylyuk; Albert V Davydov; Ruixing Zhang; Kang L Wang

doi:10.1038/s41467-023-42447-4

Emergent ferromagnetism with superconductivity in Fe(Te,Se) van der Waals Josephson junctions

Nat Commun. 2023 Oct 23;14(1):6691. doi: 10.1038/s41467-023-42447-4.

Authors

Gang Qiu^#¹, Hung-Yu Yang^#², Lunhui Hu³, Huairuo Zhang^{4

5}, Chih-Yen Chen⁶, Yanfeng Lyu⁷, Christopher Eckberg^{2

8

9

10}, Peng Deng^{2

11}, Sergiy Krylyuk⁴, Albert V Davydov⁴, Ruixing Zhang³, Kang L Wang¹²

Affiliations

¹ Department of Electrical and Computer Engineering, University of California, Los Angeles, CA, 90095, USA. gqiu@g.ucla.edu.
² Department of Electrical and Computer Engineering, University of California, Los Angeles, CA, 90095, USA.
³ Department of Physics & Astronomy, The University of Tennessee, Knoxville, Knoxville, TN, 37996, USA.
⁴ Materials Science and Engineering Division, National Institute of Standards and Technology (NIST), Gaithersburg, MD, 20899, USA.
⁵ Theiss Research, Inc, La Jolla, CA, 92037, USA.
⁶ Department of Electrophysics, National Yang Ming Chiao Tung University (NYCU), Hsinchu, 30010, Taiwan.
⁷ School of Science, Nanjing University of Posts and Telecommunications, 210023, Nanjing, China.
⁸ Fibertek Inc, Herndon, VA, 20171, USA.
⁹ DEVCOM Army Research Laboratory, Adelphi, MD, 20783, USA.
¹⁰ DEVCOM Army Research Laboratory, Playa Vista, Los Angeles, CA, 90094, USA.
¹¹ Beijing Academy of Quantum Information Sciences, 100193, Beijing, China.
¹² Department of Electrical and Computer Engineering, University of California, Los Angeles, CA, 90095, USA. wang@ee.ucla.edu.

^# Contributed equally.

Abstract

Ferromagnetism and superconductivity are two key ingredients for topological superconductors, which can serve as building blocks of fault-tolerant quantum computers. Adversely, ferromagnetism and superconductivity are typically also two hostile orderings competing to align spins in different configurations, and thus making the material design and experimental implementation extremely challenging. A single material platform with concurrent ferromagnetism and superconductivity is actively pursued. In this paper, we fabricate van der Waals Josephson junctions made with iron-based superconductor Fe(Te,Se), and report the global device-level transport signatures of interfacial ferromagnetism emerging with superconducting states for the first time. Magnetic hysteresis in the junction resistance is observed only below the superconducting critical temperature, suggesting an inherent correlation between ferromagnetic and superconducting order parameters. The 0-π phase mixing in the Fraunhofer patterns pinpoints the ferromagnetism on the junction interface. More importantly, a stochastic field-free superconducting diode effect was observed in Josephson junction devices, with a significant diode efficiency up to 10%, which unambiguously confirms the spontaneous time-reversal symmetry breaking. Our work demonstrates a new way to search for topological superconductivity in iron-based superconductors for future high T_c fault-tolerant qubit implementations from a device perspective.

Abstract

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