Supercurrent Diode Effect, Spin Torques, and Robust Zero-Energy Peak in Planar Half-Metallic Trilayers

Klaus Halterman; Mohammad Alidoust; Ross Smith; Spencer Starr

doi:10.1103/PhysRevB.105.104508

paper

Supercurrent Diode Effect, Spin Torques, and Robust Zero-Energy Peak in Planar Half-Metallic Trilayers

arXiv:2111.01242 · doi:10.1103/PhysRevB.105.104508

Abstract

We consider a Josephson junction with $F_{1} F_{2} F_{3}$ ferromagnetic trilayers in the ballistic regime, where the magnetization in each ferromagnet $F_{i} (i = 1, 2, 3)$ , can have arbitrary orientations and magnetization strengths. The trilayers are sandwiched between two $s$ -wave superconductors with a macroscopic phase difference $Δ φ$ . A broad range of magnetization strengths of the central $F_{2}$ layer are considered, from an unpolarized normal metal (N) to a half-metallic phase, supporting only one spin species. Our results reveal that when the magnetization configuration in $F_{1} F_{2} F_{3}$ has three orthogonal components, a supercurrent can flow at $Δ φ = 0$ , and a strong second harmonic in the current-phase relation appears. Upon increasing the magnetization strength in the central ferromagnet layer up to the half-metallic limit, the self-biased current and second harmonic component become dramatically enhanced, and the critical supercurrent reaches its maximum value. The higher harmonics in the current-phase relations can be controlled by the relative magnetization orientations, with negligible current damping compared to the corresponding $F_{1} N F_{3}$ counterparts. For a broad range of exchange field strengths in the central ferromagnet $F_{2}$ , the ground state of the system can be tuned to an arbitrary phase difference $φ_{0}$ by rotating the magnetization in the outer ferromagnet $F_{3}$ . For intermediate exchange field strengths in $F_{2}$ , a $φ_{0}$ state can arise that creates a superconducting diode effect, whereby $Δ φ$ can be tuned to create a one-way dissipationless current flow. The density of states demonstrates the emergence of zero energy peaks for the mutually orthogonal magnetization configurations, which is strongest in the half-metallic phase.

Supercurrent Diode Effect, Spin Torques, and Robust Zero-Energy Peak in Planar Half-Metallic Trilayers

Abstract

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