High bias anomaly in YBa2Cu3O7/LaMnO_{3+delta}/YBa2Cu3O7 Superconductor/Ferromagnetic Insulator/Superconductor junctions: Evidence for a long-range superconducting proximity effect through the conduction band of a ferromagnetic insulator

Abstract

We study the perpendicular transport characteristics of small superconductor/ferromagnetic insulator/superconductor (YBa${}_2$Cu${}_3$O${}_{7-x}$/LaMnO${}_{3+\delta }$/YBa${}_2$Cu${}_3$O${}_{7-x}$) tunnel junctions. At a large bias voltage $V\sim 1$ V we observe a step-like onset of excess current that occurs below the superconducting transition temperature $T<T_c$ and is easily suppressed by a magnetic field. The phenomenon is attributed to a novel type of the superconducting proximity effect of non-equilibrium electrons injected into the conduction band of the ferromagnetic insulator via a Fowler-Nordheim tunneling process. The occurrence of a strongly non-equilibrium population is confirmed by the detection of photon emission at large bias voltage. Since the conduction band in our ferromagnetic insulator is strongly spin polarized, the long-range (20 nm) of the observed proximity effect provides evidence for an unconventional spin-triplet superconducting state.

12 pages, 6 figures

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Cited by in corpus (11)

• Influence of La and Mn vacancies on the electronic and magnetic properties of LaMnO${}_3$ thin films grown by pulsed laser deposition
• Controllable generation of a spin-triplet supercurrent in a Josephson spin-valve
• X-ray absorption study of the ferromagnetic Cu moment at the $\mathbf{YB}{\mathbf{a}}_2\mathbf{C}{\mathbf{u}}_3{\mathbf{O}}_7/\mathbf{L}{\mathbf{a}}_{2/3}\mathbf{C}{\mathbf{a}}_{1/3}\mathbf{Mn}{\mathbf{O}}_3$ interface and the variation of its exchange interaction with the Mn moment
• Crossover between short and long range proximity effects in SFS junctions with Ni-based ferromagnets
• Controlling the strength of ferromagnetic order in YBa${}_2$Cu${}_3$O${}_7$/La${}_{2/3}$Ca${}_{1/3}$MnO${}_3$ multilayers
• X-ray absorption spectroscopy study of the electronic and magnetic proximity effects in YBa${}_2$Cu${}_3$O${}_7$/La${}_{2/3}$Ca${}_{1/3}$MnO${}_3$ and La${}_{2-x}$Sr${}_x$CuO${}_4$/La${}_{2/3}$Ca${}_{1/3}$MnO${}_3$ multilayers
• YBa2Cu3O7/LaXMnO3 (X: Ca, Sr) based Superconductor/Ferromagnet/Superconductor junctions with memory functionality
• Backfolded acoustic phonons in metal-oxide superlattices
• Heat transport and electron cooling in ballistic normal-metal/spin-filter/superconductor junctions
• Modeling Tunneling for the Unconventional Superconducting Proximity Effect
• Andreev Reflection without Fermi surface alignment in High T${}_c$-Topological heterostructures