Short-range spectroscopic signatures of spin-triplet proximity effect on (110) La_2/3Ca_1/3MnO₃/YBa₂Cu₃O_7-δ bilayers

This work examines the superconductor/ferromagnet (S/F) proximity effect (PE) involved in the long-range (~1 μm) S/F/S Josephson effects recently reported in lateral cuprate/manganite/cuprate heterostructures [1]. We focus on the PE along [110], a crucial in-plane direction because of the d-wave pairing and anisotropic band structure of cuprates. Scanning tunneling spectroscopy is performed on epitaxial (110) bilayers of La_2/3Ca_1/3MnO₃/YBa₂Cu₃O_7-δ at 4.2 K. The data is analyzed with PE theory of pairing symmetry classes in different scattering regimes [2,3], to infer the presence of spin-triplet pairs in the half-metallic manganite layer. At 3 nm and 5 nm layer thickness, dI/dV spectra show zero-bias Andreev resonances attributed to odd-frequency equal-spin-triplet pairing, but no signatures of PE appear at 10 nm. The PE length scale (≤ 10 nm) determined from our data, and those from prior data along [100] and [001], are too short to explain the long-range Josephson effects.

[1] D. Sanchez-Manzano et al., Nat. Mater. 21, 188 (2022)

[2] T. Yokoyama et al., Phys. Rev. B 75, 134510 (2007).

[3] J. Linder et al., Phys. Rev. B 79, 064514 (2009).