Van der Waals pi Josephson junctions

Abstract

Proximity-induced superconductivity in a ferromagnet can induce Cooper pairs with a finite center-of-mass momentum. The resultant spatially modulated superconducting order parameter is able to stabilize Josephson junctions (JJs) with pi phase difference in superconductor-ferromagnet heterostructures and realize 'quiet' phase qubits. The emergence of two-dimensional (2D) layered superconducting and magnetic materials promises a new platform for realizing pi JJs with atomically sharp interfaces by van der Waals stacking. Here we demonstrate a thickness-driven 0-pi transition in JJs made of NbSe2 (an Ising superconductor) with a Cr2Ge2Te6 (a ferromagnetic semiconductor) weak link. By systematically varying the Cr2Ge2Te6 thickness, we observe a vanishing supercurrent at a critical thickness around 8 nm, followed by a re-entrant supercurrent upon further increase in thickness. Near the critical thickness, we further observe unusual supercurrent interference patterns with vanishing critical current around zero in-plane magnetic field. They signify the formation of 0-pi JJs (with both 0 and pi regions) likely induced by the nanoscale magnetic domains in Cr2Ge2Te6. Our work highlights the potential of van der Waals superconductor-ferromagnet heterostructures for the explorations of unconventional superconductivity and superconducting electronics.

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References in corpus (7)

• Highly crystalline 2D superconductors
• 0-pi Josephson tunnel junctions with ferromagnetic barrier
• High quality ferromagnetic 0 and pi Josephson tunnel junctions
• Penetration depth study of superconducting gap structure of 2\textit{H}-NbSe${}_2$
• Tuning of Magnetic Activity in Spin-Filter Josephson Junctions Towards Spin-Triplet Transport
• Josephson current in a superconductor -- ferromagnet -- superconductor junction with in-plane ferromagnetic domains
• Giant anisotropic magnetoresistance in Ising superconductor-magnetic insulator tunnel junctions

Cited by in corpus (12)

• Ferromagnetic Materials for Josephson π Junctions
• Evidence for $\pi$-shifted Cooper quartets and few-mode transport in PbTe nanowire three-terminal Josephson junctions
• Ising superconductivity: a first-principles perspective
• Controllable magnetic states in chains of coupled phi-0 Josephson junctions with ferromagnetic weak links
• Signature of long-ranged spin triplets across a two-dimensional superconductor/helimagnet van der Waals interface
• Flux-pinning mediated superconducting diode effect in the NbSe${}_2$/CrGeTe${}_3$ heterostructure
• Gate-tunable nonlocal Josephson effect through magnetic van der Waals bilayers
• Voltage-driven dynamics of ${\phi }_0$-S/F/S Josephson junctions chains
• Engineering Ponderomotive Potential for Realizing $\pi$ and $\pi /2$ Bosonic Josephson Junctions
• Building 3D superconductor-based Josephson junctions using a via transfer approach
• Odd-frequency Pairing in Josephson Junctions Coupled by Magnetic Textures
• Specular-Andreev reflection and Andreev interference in an Ising superconductor junction