Generation and manipulation of light-induced orbital transport in Co/Zr/Al2O3 heterostructure probed with ultrafast terahertz emission
H. F. Xu, Yuhe R. Yang, Zuanming Jin, Ping Wang, Zheng Feng, Ting Wang, Wensi Yue, Cheng Chen, Feng Chen, Yiming Zhu, Yan Peng, Delin Zhang, Yong Jiang, Songlin Zhuang
Abstract
The utilization of terahertz (THz) emission spectroscopy in femtosecond photoexcited spintronic heterostructures has emerged as a versatile tool for investigating ultrafast spin-transport in a non-contact and non-invasive manner. However, the investigation of ultrafast orbital-transport is still in the primitive stage. Here, we experimentally demonstrate the orbital-to-charge current conversion in Co/Zr/Al2O3 heterostructures. Our experimental results indicate a photoinduced orbital current (JL) from Co propagating through Zr layer with a long-distance ballistic transport and a velocity of ~ $$0.27$$ ± $$0.02 \, {{\rm{nm}}} \, {{{\rm{fs}}}}^{-1}$$ . On the one hand, we demonstrate a critical pump fluence required to overcome the collisions in orbital transport, enabling a swifter flow of JL. On the other hand, a critical temperature is observed, below which the orbital transport is impeded. Finally, we observe a nearly 2.95-fold enhancement in the THz emission due to an additional conversion of the spin-to-orbital current conversion from a 1 nm thick W-insertion layer between Co and Zr layers. Our results pave the way for designing promising opto-spin-orbitronic devices and THz emitters. Efficient generation, manipulation, detection of orbital current and its interconversion to charge current are key to developing orbital current-based spintronic devices. This study demonstrates ultrashort laser pulse-induced efficient generation of orbital current in Co/Zr/Al2O3 heterostructures and its conversion to charge current by inverse orbital Hall and Rashba-Edelstein effects.