Affiliation
Max Planck Institute of Microstructure Physics
Title
Non-reciprocity of critical supercurrent in 2D van der Waals based Josephson Junctions
Abstract
Recently we have discovered a non-reciprocal Josephson diode effect in several Josephson junctions, both lateral and vertical, formed from conventional superconducting electrodes (Nb, NbSe2) separated by several non-superconducting metals including the 2D van der Waals metals, NiTe2 [1] and WTe2 [2], as well as sputtered layers of platinum that are magnetically proximitized via a magnetic insulator (YIG) [3]. Each of these materials becoming superconducting by proximity to the conventional superconducting electrodes. The superconductivity can be sustained over long distances of, in some cases, up to ~1 micron. The critical supercurrent densities for current flowing in opposite directions within the junction are distinct and can vary by up to 40% or more. For the van der Waals metals the non-reciprocity is only observed in the presence of a small magnetic field oriented perpendicular to the supercurrent, whereas for the Pt based junctions the diode effect is observed in zero field. For vertical Josephson junctions formed from WTe2 we show that the non-reciprocity depends on the orientation of the magnetic field with respect to the crystal structure of the WTe2, proving thereby the intrinsic origin of the Josephson diode effect. We also show how the magnitude of the asymmetry increases with the thickness of the WTe2 barrier[2]. Finally, we discuss our recent work on spin-triplet supercurrent spin valves using 2D chiral Kagome antiferromagnets [4].
[1] B. Pal et al., "Josephson diode effect from Cooper pair momentum in a topological semimetal," Nat. Phys., vol. 18, pp. 1228-1233, 2022.
[2] J.-K. Kim et al., "Intrinsic supercurrent non-reciprocity coupled to the crystal structure of a van der Waals Josephson barrier," arXiv:2303.13049, 2023.
[3] K.-R. Jeon et al., "Zero-field polarity-reversible Josephson supercurrent diodes enabled by a proximity-magnetized Pt barrier," Nat. Mater., vol. 21, pp. 1008-1013, 2022.
[4] K.-R. Jeon et al., "Chiral antiferromagnetic Josephson junctions as spin-triplet supercurrent spin valves and d.c. SQUIDs," Nat. Nanotechnol., 2023.