Chiral antiferromagnetic Josephson junctions as spin-triplet supercurrent spin valves and d.c. SQUIDs

Intensive research in coupling superconducting condensate state with magnetic-exchange spin splitting have opened up a analysis area of superconducting spintronics^1,2,3, which guarantees to appreciate dissipationless spin-based logic and reminiscence applied sciences. Of explicit relevance on this analysis is the theoretical prediction^4,5,6,7 and experimental verification^8,9,10,11,12 that spin-polarized triplet pairing states may be created by way of spin-mixing and spin-rotation processes (for instance, non-collinear alternate fields^4,5,6,8,9,10 in actual area and/or spin–orbit fields^7,11,12 in reciprocal/ok area) at proximity-engineered superconductor/ferromagnet (FM) interfaces^{1,2,3,4,5,6,7,8,9,10,11,12}. With these advances, the sector of superconducting spintronics involving spin-polarized triplet Cooper pairs^1,2,3 can reply two sensible facets: the best way to effectively generate such triplet pairs and the best way to tune them in a controllable method. But, as beforehand identified^4,13,14, fulfilling these two necessities on the identical time appears difficult as a result of the preconfigured strong non-collinearity of spin-mixer and spin-rotator magnetizations for the next singlet-to-triplet pair conversion makes it troublesome to regulate by an exterior stimulus.

The energetic and reversible management of spin-polarized triplet supercurrents has up to now been principally achieved in ferromagnetic Josephson junctions (JJs)^13,14, the place at the very least three FMs represent a Josephson barrier whose relative magnetization instructions, and due to this fact the non-collinearity, may be managed by exterior magnetic fields^4,13,14. This has led to the so-called spin-triplet supercurrent spin valve^4,13,14, by which the proximity-created spin-polarized triplet supercurrents may be switched on and off. Nevertheless, the fabrication of such ferromagnetic spin-triplet JJs^13,14 requires delicate interface engineering, as an illustration, digital vitality band matching between neighbouring layers, selectivity in coercive fields of the spin-mixer and spin-rotator FMs and circumventing the out-of-plane (OOP) element of stray magnetic fields.

On this work, we reveal an antiferromagnetic analogue of the spin-triplet supercurrent spin-valve impact^4,13,14 by way of the usage of a single topological chiral antiferromagnet (AFM) Mn₃Ge (refs. ^15,16,17), which—with its lack of stray fields—may be extremely advantageous for growing superconducting spintronic logic circuits¹. The noteworthy side of Mn₃Ge is that its non-collinear triangular antiferromagnetic spin association^15,16,17 in actual area (Fig. 1a,b) and the fictional magnetic fields derived from Berry curvature^18,19 in ok area, that are strong to low temperature T (refs. ^15,16,17,20), facilitate the spin-mixing and spin-rotation processes^{1,2,3,4,5,6,7,8,9,10,11,12} required for singlet-to-triplet pair conversion. This allows, as proven in our latest experiment²⁰, the proximity era of long-range triplet supercurrents by way of the one chiral antiferromagnetic Josephson barrier.

a,b, Possible 120° chiral antiferromagnetic configurations and crystal construction of D0₁₉-Mn₃Ge(0001) canted out of the kagome aircraft below a perpendicular magnetic area μ₀H_⊥ (perpendicular to the a–b aircraft). Two layers of Mn and Ge atoms are stacked alongside the c axis (parallel to the z axis), the place blue and gray (pink and black circles) symbolize Mn and Ge atoms mendacity within the z = 0 (z = c/2) aircraft, respectively. c, Scanning electron micrograph of the fabricated Nb/Mn₃Ge/Nb lateral JJs. Be aware that the 5-nm-ultrathin Ru underlayer acts as a buffer layer (Strategies). Scale bar, 0.5 µm. d, Josephson crucial present I_c versus μ₀H_⊥ plot for the d_s = 199 nm Nb/Mn₃Ge/Nb JJ, taken at T = 2 Ok. Right here μ₀H_⊥ is utilized perpendicular to the kagome (interface) aircraft of the Mn₃Ge barrier (Nb electrodes) (backside inset). The highest-left inset shows the zero-field I–V curve above (8 Ok) and beneath (2 Ok) the superconducting transition of the JJ. The highest-right inset reveals the I–V curve close to the zero-order minimal of I_c(μ₀H_⊥). The strong strains correspond to our theoretical copy that takes each real-space magnetic texture (below an OOP magnetic area) and the ok-space Weyl nodes into consideration (Supplementary Part 1). e, Magnified I_c(μ₀H_⊥) plot round μ₀H_⊥ = 0 the place uneven hysteretic I_c(μ₀H_⊥) interference with the zero-order maximum-to-maximum offset Δμ₀H_⊥ = 1.0 mT is clear. The error bars in d and e symbolize the usual deviation.