Universal behaviors of magnon-mediated spin transport in disordered nonmagnetic metal-ferromagnetic insulator heterostructures
Gaoyang Li1, Fuming Xu1, Jian Wang1,2()
1. College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China 2. Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, China
We numerically investigate magnon-mediated spin transport through nonmagnetic metal/ferromagnetic insulator (NM/FI) heterostructures in the presence of Anderson disorder, and discover universal behaviors of the spin conductance in both one-dimensional (1D) and 2D systems. In the localized regime, the variance of logarithmic spin conductance σ2(lnGT) shows a universal linear scaling with its average ⟨lnGT⟩, independent of Fermi energy, temperature, and system size in both 1D and 2D cases. In 2D, the competition between disorder-enhanced density of states at the NM/FI interface and disorder-suppressed spin transport leads to a non-monotonic dependence of average spin conductance on the disorder strength. As a result, in the metallic regime, average spin conductance is enhanced by disorder, and a new linear scaling between spin conductance fluctuation rms(GT) and average spin conductance GT is revealed which is universal at large system width. These universal scaling behaviors suggest that spin transport mediated by magnon in disordered 2D NM/FI systems belongs to a new universality class, different from that of charge conductance in 2D normal metal systems.
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The Fermi energies used in scaling analysis (Fig.5 and Fig.6) are near the center of the first subband. This is the region where SPS works in normal metal system [20]. Although the ranges of Fermi energies and temperatures are not very wide, the spin conductance in Fig.5(a) varies large enough in magnitude to support our scaling analysis.
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