New Method to Detect Spin Current in Topological Insulators

New Method to Detect Spin Current in Topological Insulators

Scientific Achievement
In a spin-polarized four-probe scanning tunneling microscope, two outer probes contact the sample surface to inject charge carriers , and two inner probes, with different spin sensitivities, measure the surface potential at varying surface sites. The difference measured by two probes at the same location shows the imbalance of moving electrons with different spin orientations.  (hi-res image)

A new method that precisely measures the magnetic properties of electrons flowing across the surface of a topological insulator reveals the correlation of electron momentum and spin polarization.

Significance and Impact

The ability to directly measure the spin potential of moving electrons results in a “spin voltmeter.” These measurements are crucial for evaluating spintronic and other quantum materials. 

Research Details

- A spin-polarized four-probe scanning tunneling microscope is developed.

- This capability leads to the first direct revelation of spin-momentum locking in topological insulators.

- The current’s spin polarization is measured by comparing the potential difference acquired by a ferromagnetic and a nonmagnetic probe at the same sample location.

S. M. Hus, X.-G. Zhang, G. D. Nguyen, W. Ko, A. P. Baddorf, Y. P. Chen, A.-P. Li. Phys. Rev. Lett., 119, 137202 (2017).   DOI: 10.1103/PhyRevLett.119.137202


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