Possibility of Observing Spin-Polarized Tunneling Current Using Scanning Tunneling Microscope with Optically Pumped GaAs

Abstract

A scanning tunneling microscope (STM) experiment demonstrating the spin-polarized tunneling effect was performed. A GaAs thin-film sample pumped by circularly polarized light, and a ferromagnetic polycrystalline Ni tip are used. The tunneling current is perturbed by modulating the power and polarization of the pumping light. The perturbation arises due to three dominant effects: the thermal expansion of the tip or sample, the variation in excited carrier concentration in GaAs and the spin-polarized tunneling effect. The spin-polarized effect can be distinguished by observing the current dependence on the bias. Well-adjusted pumping optics allows the separate detection of the spin-polarized signal, which depends upon the circular polarization of the light and the tip magnetization. The present experiment indicates the feasibility of a spin-polarized STM with a non-magnetic tip.