Peculiar spin texture of Bi(110) observed by ESPRESSO machine

Bismuth is one of the prototypical materials showing clear spin-polarization by spin-orbit interaction. Especially Bi(111) surface has been investigated extensively as a demonstrative Rashba spin-split system and the characteristic spin texture including out-of-plane spin components caused by the higher order Rashba Hamiltonian has been unveiled [1,2] Compared with Bi(111) surface, Bi(110) surface had not got much attention until recently. Several metallic surface electronic bands giving rise to a complex Fermi surface were first reported by ARPES observation[3]. The first principles calculation has suggested the complex in-plane spin texture of the Fermi surface, and the quasi-particle interference (QPI) pattern by STM is in fair agreement with the calculated spin texture[4,5]. However, the direct observation of spin texture by spin-resolved AREPS (SARPES) has not yet been reported on the Bi(110) surface.
In this presentation, we present the peculiar spin texture of the Bi(110) surface that is obtained by the ESPRESSO machine[6], a high-resolution SARPES machine at our facility. By utilizing the three-dimensional spin vector analysis, comprehensive spin texture with not only the in-plane spin component that is basically consistent with the spin textures proposed by previous QPI measurements but also significant out-of-plane spin polarization has been experimentally revealed. The peculiar spin texture which is caused by the low symmetry (C1h) and pseudocubic surface structure of Bi(110) surface, can be in principle reproduced by our first principles calculation but some deviation has been also evidenced especially in the out-of-plane spin component in which the periodicity of the spin texture in k-space does not follow the periodicity of surface Brillouin zone.

References
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