Ultrafast THz probing of nonlocal orbital current in transverse multilayer metallic heterostructures

Abstract

THz generation from femtosecond photoexcited spintronic heterostructures has become a versatile tool for investigating ultrafast spin-transport and transient charge-current in a non-contact and non-invasive manner. The equivalent effect from the orbital degree of freedom is still in the primitive stage. Here, we experimentally demonstrate orbital-to-charge current conversion in metallic heterostructures, consisting of a ferromagnetic layer adjacent to either a light or a heavy metal layer, through detection of the emitted THz pulses. Our temperature-dependent experiments help to disentangle the orbital and spin components that are manifested in the respective Hall-conductivities, contributing to THz emission. NiFe/Nb shows the strongest inverse orbital Hall effect with an experimentally extracted value of effective intrinsic Hall-conductivity, $${({\sigma }_{{SOH}}^{{{{{\mathrm{int}}}}}})}^{{eff}} \sim 195{\varOmega }^{-1}{{cm}}^{-1}$$ ( σ S O H int ) e f f ~ 195 Ω − 1 c m − 1 , while CoFeB/Pt shows maximum contribution from the inverse spin Hall effect. In addition, we observe a nearly ten-fold enhancement in the THz emission due to pronounced orbital-transport in W-insertion heavy metal layer in CoFeB/W/Ta heterostructure as compared to CoFeB/Ta bilayer counterpart.

Promoting overall sulfur redox kinetics for Li–S batteries via interfacial synergy in a NiS–NiTe2 heterostructure-modified separator

“…In recent years, there has been growing attention to the application of heterogeneous structure materials in catalysis, energy, and other fields. 28–32 Heterogeneous structures are defined as a novel class of materials composed of distinct regions with different physical properties. The mutual coupling between these heterogeneous regions can generate synergistic effects, resulting in comprehensive performance that far surpasses that of simple mixed materials, showcasing physical and chemical properties not found in traditional homogeneous materials.…”

Active ballistic orbital transport in Ni/Pt heterostructure

“…Recent research has proposed that orbital transport can be ballistic and can propagate over long distance, reaching up to 80 nm in some of the widely used nonmagnetic layers like Tungsten (W) at a velocity measured up to 0.14 nm/fs 25 . Various other works have also described a long-range transport of orbital current in several metals 26 – 28 including via THz emission 29 .

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