Highly Efficient Multichannel Spin-Polarization Detection

Since the original work by Mott, the low efficiency of electron spin polarimeters, remaining orders of magnitude behind optical polarimeters, has prohibited many fundamental experiments. Here we report a solution to this problem using a novel concept of multichannel spin-polarization analysis that provides a stunning increase in efficiency by 4 orders of magnitude. This improvement was demonstrated in a setup using a hemispherical electron energy analyzer. An imaging setup proved the principal capability of resolving more than ${10}^5$ data points in parallel.

Figure 1

(a) Schematic view of the multichannel spin polarimeter setup behind the exit field of a hemispherical analyzer comprising a narrow entrance slit and a wide exit field. Two of the trajectory bundles indicate electron paths separated along the energy axis $E_i$. The other bundles correspond to different emission angles separated along the ${\Theta }_j$ axis on the detector. (b) Geometry of the scattering process for simultaneous acquisition of 16 data points for the idealized case of a parallel beam and (c) corresponding momentum scheme (Ewald construction) in the kinematic approximation for specular reflection [(0,0) beam] for W(100) at 45° and 26 eV. A variation of $E$ by 10% modifies the scattering condition (red).

Figure 2

(a) Two-dimensional electron intensity distribution (false color map) in the exit field of the electron spectrometer, imaged after reflection at the spin filter crystal. The spectrum corresponds to the 2D photoelectron distribution of an iron film near the Fermi edge ($h\nu =21.23\mathrm{eV}$). (b) Corresponding asymmetry pattern calculated from two measurements with opposite magnetization directions of the iron film, cf. Eq. (1). The background was corrected linearly, the intensity variation in the dependence of $\Theta$ was not corrected. (c) Line scans of the asymmetry for different angular coordinates ${\Theta }_j$.

Figure 3

Spin-resolved spectra ($h\nu =21.23\mathrm{eV}$) near the Fermi edge of a clean Fe(100) surface. The up (down) arrow denotes majority (minority) partial spectra.