Direct penetration of spin-triplet superconductivity into a ferromagnet in Au/SrRuO3/Sr2RuO4 junctions

Abstract

Efforts have been ongoing to establish superconducting spintronics utilizing ferromagnet/superconductor heterostructures. Previously reported devices are based on spin-singlet superconductors (SSCs), where the spin degree of freedom is lost. Spin-polarized supercurrent induction in ferromagnetic metals (FMs) is achieved even with SSCs, but only with the aid of interfacial complex magnetic structures, which severely affect information imprinted to the electron spin. Use of spin-triplet superconductors (TSCs) with spin-polarizable Cooper pairs potentially overcomes this difficulty and further leads to novel functionalities. Here, we report spin-triplet superconductivity induction into a FM SrRuO3 from a leading TSC candidate Sr2RuO4, by fabricating microscopic devices using an epitaxial SrRuO3/Sr2RuO4 hybrid. The differential conductance, exhibiting Andreev-reflection features with multiple energy scales up to around half tesla, indicates the penetration of superconductivity over a considerable distance of 15 nm across the SrRuO3 layer without help of interfacial complex magnetism. This demonstrates potential utility of FM/TSC devices for superspintronics.

High-Resolution Photoemission on Sr2RuO4 Reveals Correlation-Enhanced Effective Spin-Orbit Coupling and Dominantly Local Self-Energies

“…Its intriguing superconducting ground state, sharing similarities with superfluid 3 He [1][2][3], has attracted much interest and continues to stimulate advances in unconventional superconductivity [4]. Experimental evidence suggest odd-parity spin-triplet pairing, yet questions regarding the proximity of other order parameters, the nature of the pairing mechanism and the apparent absence of the predicted edge currents remain open [3][4][5][6][7][8][9]. Meanwhile, the normal state of Sr 2 RuO 4 attracts interest as one of the cleanest oxide Fermi liquids [10][11][12][13].…”

Half-metallic superconducting triplet spin multivalves

“…If differing ferromagnetic materials, constituting the left and right F layers are chosen properly, they respond to an external magnetic field in different ways, providing active control of the magnetization misalignment angles through variations in the intensity and direction of an external magnetic field. It was shown that the superconducting transition temperature [46][47][48][49][50] and density of states 13,[51][52][53][54] reveal prominent signatures of the long-ranged spin-triplet superconductivity 5 as a function of magnetization misalignment. Nevertheless, a direct and clear observation of the equal-spin triplet pairings in superconducting hybrids is still elusive.…”

Strong peak in T c of Sr 2 RuO 4 under uniaxial pressure

“…Knight shift measurements [12,13] and, recently, proximity-induced superconductivity in epitaxial ferromagnetic SrRuO 6 layers [14] provide strong evidence for triplet pairing. Muon spin rotation [15] and Kerr rotation [16] experiments point to time reversal symmetry breaking at…”