Spin-to-Charge Conversion Manipulated by Fine-Tuning the Fermi Level of Topological Insulator (Bi1–xSbx)2Te3

The efficiency of spin-to-charge conversion is a key parameter in determining the performance of emerging spintronic devices. In the topological surface state of a topological insulator (TI), the spin-momentum locking effect offers a great possibility for efficient spin-to-charge conversion. Here, we report the relation between the Fermi level position E F and spin-to-charge conversion efficiency in heterostructure Ni 80 Fe 20 (Py)/(Bi 1– x Sb x ) 2 Te 3 . The band structure of (Bi 1– x Sb x ) 2 Te 3 films becomes tailored by tuning the ratio of bismuth to antimony so that the position of the Fermi level E F varies from the top side of the valence band to the bottom side of the conduction band through the in-gap surface Dirac cone. The result is consistent with the electronic behavior of the majority carriers varying from n-type to p-type. In spin-pumping measurements, we observed that the inverse Edelstein effect length (λ IEE ) with a tuned E F near the Dirac point is significantly enhanced, indicating that the spin-charge conversion is determined mainly by the topological surface state. These results demonstrate that fine-tuning of E F in a TI-based heterostructure is critical to maximizing the efficiency of spin-to-charge conversion using a spin-momentum locking mechanism.