Spin holography

The interference of the directly emitted photoelectron wave and the wave\nscattered coherently by neighboring atoms gives holographic fringes in the\nphotoelectron emission intensity $I(\\hat{\\bf R})$. In the electron emission\nholography technique in surface physics, $I(\\hat{\\bf R})$ is inverted\nholographically to give a 3D-image of the environment of the source atom.\nEarlier, we pointed out that the polarization pattern ${\\bf P}(\\hat{\\bf R})$\nsimilarly can be viewed as a hologram of the spin environment of the source\natom by virtue of the exchange scattering of the photoelectron by the\nneighboring atoms. In this paper, we point out that spin-orbit correlations in\nthe photoelectron initial state are responsible for holographic spin-dependent\ncontributions to the intensity hologram $I(\\hat{\\bf R})$, even if the directly\nemitted photoelectrons are unpolarized. This remarkable result implies that the\nemission intensity contains spin information just as the polarization pattern\n${\\bf P}(\\hat{\\bf R})$. Although the spin dependent signal in the hologram is\nrather small ($\\sim 5 \\% $ in most cases of interest), we show how spin\ninformation can be extracted from the intensity hologram, making use of the\npoint symmetry of the environment of the source atom. This way of analyzing\nphotoelectron intensity holograms to extract short-range spin information opens\nup a new avenue for surface magnetism studies.\n