Direct observation of spin splitting in bismuth surface states

Received 6 April 2007; revised manuscript received 21 May 2007; published 12 October 2007The electronic structure of ultrathin Bi 001 filmsonSi 111 -7 7 was studied by spin and angle-resolvedphotoemission spectroscopy. We directly observed a clear momentum-dependent spin splitting and polarizationof the surface-state bands. The spin structure was antisymmetric with respect to the ¯ point as predicted bytheory, and the obtained in-plane spin polarization was as high as ±0.5. The qualitative features of the observedspin polarization are discussed in comparison with the spin-polarized band structure obtained by first-principlescalculations.DOI: 10.1103/PhysRevB.76.153305 PACS number s : 79.60.Bm, 68.35. p, 73.20. r, 85.75. d

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