Signature of magnetic-dependent gapless odd frequency states at superconductor/ferromagnet interfaces
arXiv:1609.02905 · doi:10.1038/ncomms9053
Abstract
The theory of superconductivity developed by Bardeen, Cooper and Schrieffer (BCS) explains the stabilization of electron pairs into a spin-singlet, even frequency, state by the formation of an energy gap within which the density of states is zero. At a superconductor interface with an inhomogeneous ferromagnet, a gapless odd frequency superconducting state is predicted, in which the Cooper pairs are in a spin-triplet state. Although indirect evidence for such a state has been obtained, the gap structure and pairing symmetry have not so far been determined. Here we report scanning tunnelling spectroscopy of Nb superconducting films proximity coupled to epitaxial Ho. These measurements reveal pronounced changes to the Nb subgap superconducting density of states on driving the Ho through a metamagnetic transition from a helical antiferromagnetic to a homogeneous ferromagnetic state for which a BCS-like gap is recovered. The results prove odd frequency spin-triplet superconductivity at superconductor/inhomogeneous magnet interfaces.
References in corpus (6)
- Evidence for Triplet Superconductivity in a Superconductor-Ferromagnet Spin Valve
- Manifestation of the odd-frequency spin-triplet pairing state in diffusive ferromagnet / superconductor junctions
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- Unconventional superconductivity induced in Nb films by adsorbed chiral molecules
- Generalized quasiclassical theory of the long-range proximity effect and spontaneous currents in superconducting heterostructures with strong ferromagnets
- Multiple odd-frequency superconducting states in buckled quantum spin Hall insulators with time-reversal symmetry
- Spin-triplet supercurrent in Josephson junctions containing a synthetic antiferromagnet with perpendicular magnetic anisotropy
- Nonuniform superconductivity and Josephson effect in conical ferromagnet
- Gapped superconductivity with all symmetries in InSb (110) quantum wells in proximity to s-wave superconductor in Fulde-Ferrell-Larkin-Ovchinnikov phase or with a supercurrent
- Symmetry analysis of odd- and even-frequency superconducting gap symmetries for time-reversal symmetric interactions
- Long-range triplet proximity effect in multiply connected ferromagnet-superconductor hybrids
- Signatures of spin-triplet Cooper pairing in the density of states of spin-textured superconductor-ferromagnet bilayers
- Quantum kinetic equations and anomalous non-equilibrium Cooper pair spin accumulation in Rashba wires with Zeeman splitting
- Magnetic-field-orientation-dependent triplet supercurrents in Josephson junctions with symmetric and asymmetric exchange-spring interfaces