Detection of the Spin-Chemical Potential in Topological Insulators Using Spin-Polarized Four-Probe STM

Saban M Hus; X-G Zhang; Giang D Nguyen; Wonhee Ko; Arthur P Baddorf; Yong P Chen; An-Ping Li

doi:10.1103/PhysRevLett.119.137202

Detection of the Spin-Chemical Potential in Topological Insulators Using Spin-Polarized Four-Probe STM

Phys Rev Lett. 2017 Sep 29;119(13):137202. doi: 10.1103/PhysRevLett.119.137202. Epub 2017 Sep 27.

Authors

Saban M Hus¹, X-G Zhang², Giang D Nguyen¹, Wonhee Ko¹, Arthur P Baddorf¹, Yong P Chen³, An-Ping Li¹

Affiliations

¹ Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
² Department of Physics and the Quantum Theory Project, University of Florida, Gainesville, Florida 32611, USA.
³ Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA.

PMID: 29341679
DOI: 10.1103/PhysRevLett.119.137202

Abstract

We demonstrate a new method for the detection of the spin-chemical potential in topological insulators using spin-polarized four-probe scanning tunneling microscopy on in situ cleaved Bi_{2}Te_{2}Se surfaces. Two-dimensional (2D) surface and 3D bulk conductions are separated quantitatively via variable probe-spacing measurements, enabling the isolation of the nonvanishing spin-dependent electrochemical potential from the Ohmic contribution. This component is identified as the spin-chemical potential arising from the 2D charge current through the spin momentum locked topological surface states (TSS). This method provides a direct measurement of spin current generation efficiency and opens a new avenue to access the intrinsic spin transport associated with pristine TSS.