Controlling Terahertz Spintronic Photocurrents in 2D-Semiconductor|Ferromagnet Heterostructures through a Functional Hybrid Interface

TL;DR

This study reveals that interfacial hybridization in 2D TMD|ferromagnet heterostructures enables efficient ultrafast photocurrent generation, independent of photon energy, with implications for high-speed spintronic applications.

Contribution

It uncovers a new interfacial hybridization mechanism that enhances terahertz spin and charge currents in 2D material/ferromagnet heterostructures, regardless of photon energy.

Findings

Interfacial hybrid metallic layer forms at MoS2/Co boundary.

Hybrid layer acts as a pump-energy transducer.

Current dynamics are identical above and below MoS2 band gap.

Abstract

A profound understanding of terahertz (THz) spin and charge currents in heterostructures involving ferromagnets (FMs) and two-dimensional (2D) materials promises emerging applications in high-speed sensing and data processing. Yet, ultrafast experimental insights remain very limited. Here, we study the efficient photo-generation of THz spin and charge currents in bilayers made from the transition-metal dichalcogenide (TMD) MoS2 and the FM Co. We find that the efficiency of current generation strongly depends on the pump photon energy, as previously reported. Surprisingly, however, we observe that the current dynamics remain identical for pump photon energies above and below the MoS2 band gap. Supported by ab-initio calculations, we conclude that an interfacial hybrid metallic layer forms at the MoS2/Co boundary that has a pronounced photon-energy-dependent absorptance. Thus, the hybrid interfacial layer effectively acts like a pump-energy transducer that increases the spin-current generated in the nearby Co. Our results uncover the vital role of interfacial hybridization as a yet unexplored mechanism for efficient generation of ultrafast photocurrents in 2D-TMD|FM structures.