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Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser
Published on: June 28, 2018
Unveiling the Hidden Spin-Polarized Bi(110) Surface States by Spin-Resolved Photoemission
Taichi Okuda1,2,3, Tatsuya Shishidou4, Munisa Nurmamat1
1Hiroshima University, Research Institute for Synchrotron Radiation Science (HiSOR), 2-313 Kagamiyama, Higashi-Hiroshima 739-0046, Japan.
None:
The full three-dimensional spin texture of the Bi(110) surface states has been investigated by means of spin- and angle-resolved photoemission spectroscopy. The observed complex in-plane spin texture is in basic agreement with the prior reports and first-principles calculations, and the previously unreported out-of-plane spin polarization (P_{Z}) is observed to be substantial. More significantly, the P_{Z} texture exhibits an unexpected breaking of spin degeneracy at the Brillouin zone boundary, in contradiction to standard symmetry-based expectations. Our first-principles calculations reveal that the anticipated vanishing of P_{Z} arises from the quantum interference between two surface wave functions propagating with opposite out-of-plane spin polarizations. These findings strongly suggest that the photoemission process selectively probes one of them, exposing the hidden P_{Z} polarization of the surface wave function; i.e., the apparent spin vanishing is not due to an absence of polarization, but rather results from interference at the wave function level.
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