A Multi-Probe STM Quest for Topological Surface Conductance.

An-Ping Li

Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

Topological insulators (TIs) have emerged as a new class of matter with nontrivial surface states, where a spin-momentum locking does not only provide a topological protection against backscattering but also ensures a spin-polarized surface conductance. The electrical detection of such a spin-momentum-locking, however, remains elusive. There is a lack of technique to measure the spin current, and furthermore the separation of surface conductance from often unavoidable bulk contributions remains challenging in transport experiment. In this talk, I will report a method that combines spin-polarized STM and a novel four-probe transport spectroscopy scheme to quantitatively measure spin polarization of the currents associated with the topological surface states (TSS) in TIs. The work demonstrates the unique capability of multi-probe STM and the potential of utilizing TSS for spintronic devices.

This research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.