Spin-polarized scanning tunnelling microscopy with detection of polarized luminescence emerging from a semiconductor tip

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Abstract
A variant of scanning tunnelling microscopy with spin-resolving properties, based on observation of circularly polarized luminescence from a semiconductor tip, is suggested. The method is analysed using a three-step model of electron transport, including tunnelling from a ferromagnetic sample to the tip through the vacuum gap, ballistic transport through the band-bending region of the tip subsurface and radiative recombination with holes in the semiconductor bulk. The tunnelling of spin-polarized electrons is treated with the transfer-Hamiltonian method. Then the model reveals a close connection between the degree of circular polarization of the light and the local spin polarization of the sample surface: namely, by making measurements with photons propagating in three non-collinear directions it would be possible to obtain a complete map of the distribution of surface spins with high spatial resolution without affecting the magnetization of the surface. The possibility of practical realization of such experiments is discussed.