0-π transition and 0-π Josephson junctions in van der Waals superconductor-ferromagnet heterostructures
ORAL
Abstract
Superconductor-ferromagnet heterostructures provide a promising platform to explore both unconventional superconductivity for fundamental physics and new superconducting device concepts for quantum technology. Examples include FFLO (Fulde–Ferrell–Larkin–Ovchinnikov) physics, spin-triplet and topological superconductivity, fractional fluxons and “quiet” phase qubits. The emergence of van der Waals (vdW) superconductors and magnets, which can form atomically sharp interfaces upon stacking, promises the studies of superconductor-ferromagnet heterostructures in new regimes. Here we report the fabrication of vdW Josephson junctions made of Cr2Ge2Te6 (a ferromagnetic semiconductor) sandwiched between few-layer NbSe2 (an Ising superconductor). A thickness-driven 0-π transition is observed upon increasing the layer number of Cr2Ge2Te6. Very close to the critical thickness, where the critical current density nearly vanishes, we observe the formation of 0-π Josephson junctions with uniform Cr2Ge2Te6 thickness. This is evidenced by the unusual supercurrent interference pattern that signifies regions of opposite-polarity supercurrents within the junction and the sensitivity of the interference pattern on the magnetic domain patterns. We attribute the formation of 0-π junctions to the nanoscale magnetic domain pattern in multilayer Cr2Ge2Te6, which produces spatial modulations in the 0-π transition thickness. Our work highlights the potentials of vdW superconductor-ferromagnet heterostructures in the realization of unconventional superconductivity and superconducting devices.
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Presenters
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Kaifei Kang
- Cornell University