Terahertz Spin-to-Charge Conversion by Interfacial Skew Scattering in Metallic Bilayers

Area of Science:

• Condensed matter physics
• Materials science
• Spintronics

Background:

• Efficient spin-to-charge conversion (S2C) is vital for spintronic devices.
• Heterostructure interfaces critically influence S2C efficiency.
• Understanding interfacial effects is key to advancing spin-based electronics.

Purpose of the Study:

• Investigate ultrafast S2C in various ferromagnetic/nonmagnetic (F/N) bilayers.
• Determine the impact of interface structure and material properties on S2C.
• Elucidate the mechanisms governing interfacial S2C.

Main Methods:

• Terahertz (THz) emission spectroscopy on ~50 F/N bilayers (F=NiFe, Co, Fe; N=Pt, Cu, Al).
• Systematic variation of F/N interface structures.
• Symmetry analysis and first-principles calculations.

Main Results:

• F/N interface structure drastically alters THz charge current amplitude and polarity.
• Dominant interfacial S2C observed in F/N bilayers with small spin Hall angle materials.
• Interfacial S2C contribution reached up to 20% of F/Pt reference samples.
• Skew scattering at interface imperfections identified as the primary mechanism for interfacial S2C.

Conclusions:

• Interface engineering offers a powerful route to control and enhance S2C.
• Skew scattering is a significant contributor to interfacial S2C.
• Tailored interfaces can optimize S2C across a broad frequency range (DC to THz).