Spin-to-charge conversion in ferromagnet/ topological insulator bilayers at GHz and THz frequencies

Research Focus

• Experimental studies combined with theoretical calculations of spin dynamics across a wide frequency range from ~10 GHz to several THz in a novel amorphous ferromagnet (FM)/3D topological insulator (TI) (FeGaB/BiSb) system that is scalable and provides a promising platform for spin-electronic devices.

Key Advances

• FM/TI heterostructures deposited by sputtering at room temperature.
• Ferromagnetic resonance and inverse spin-Hall effect measurements reveal interfacial spin-mixing conductance (5.03×1019 m–2), spin-diffusion length (7.86 nm), and spin-Hall angle (0.01) of BiSb.
• THz emission experiments when the bilayer is excited by femtosecond laser pulses further confirm spin-to-charge conversion in the BiSb layer.
• Kubo-Bastin formula and tight-binding model reveal thickness-dependent spin-Hall conductivity of the TI films, which agrees well with experiments.