Unconventional Fermi surface spin textures in the Bi_ {x} Pb_ {1− x}/Ag (111) surface alloy

Physical review. B, Condensed matter (Impact Factor: 3.66). 06/2009; 79(24). DOI: 10.1103/PhysRevB.79.241408
Source: arXiv

ABSTRACT The Fermi and Rashba energies of surface states in the BixPb1−x/Ag(111) alloy can be tuned simultaneously by changing the composition parameter x. We report on unconventional Fermi surface spin textures observed by spin and angle-resolved photoemission spectroscopy that are correlated with a topological transition of the Fermi surface occurring at x=0.5. We show that the surface states remain fully spin polarized upon alloying and that the spin-polarization vectors are approximately tangential to the constant energy contours. We discuss the implications of the topological transition for the transport of spin.

  • [Show abstract] [Hide abstract]
    ABSTRACT: We show, by way of tight-binding and first-principles calculations, that a one-to-one correspondence between an electron's crystal momentum k and nonzero orbital angular momentum (OAM) is a generic feature of surface bands. The OAM forms a chiral structure in momentum space much as its spin counterpart in Rashba model does, as a consequence of the inherent inversion symmetry breaking at the surface but not of spin-orbit interaction. This is the orbital counterpart of conventional Rashba effect and may be called the “orbital Rashba effect.” The circular dichroism (CD) angle-resolved photoemission (ARPES) method is an efficient way to detect this new order, and we derive formulas explicitly relating the CD-ARPES signal to the existence of OAM in the band structure. The cases of degenerate p- and d-orbital bands are considered.
    Physical review. B, Condensed matter 05/2012; 85(19). DOI:10.1103/PhysRevB.85.195401 · 3.66 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report on the observation of surface alloying and dealloying transitions during the submonolayer growth of Bi on the Cu(111) surface. In-situ scanning tunneling microscopy (STM) analysis reveals that at low coverage, and for quasi thermodynamical equilibrium, embedded Bi atoms are randomly distributed within the first Cu layer. Near the ideal coverage of 1/3, we observe an ordered BiCu2 substitutional surface alloy. Between 1/3 and 1/2 monolayer a dealloying process takes place where the surface alloy coexists with two different domains of dense Bi overlayer. In order to understand the mechanisms behind this process, the ordered alloy has been used as a template for subsequent Bi adsorption. An apparently etched surface develops during deposition and using STM image analysis, we propose that this growth mode is accompanied by a large Bi and Cu atoms redistribution inside the surface alloy.
    Surface Science 11/2013; 617:118. DOI:10.1016/j.susc.2013.06.015 · 1.87 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Microscopic mechanism for the Rashba-type band splitting is examined in detail. We show how asymmetric charge distribution is formed when local orbital angular momentum (OAM) and crystal momentum get interlocked due to surface effects. An electrostatic energy term in the Hamiltonian appears when such OAM and crystal momentum dependent asymmetric charge distribution is placed in an electric ?eld produced from an inversion symmetry breaking (ISB). Analysis by using an effective Hamiltonian shows that, as the atomic spin-orbit coupling (SOC) strength increases from weak to strong, originally OAM-quenched states evolve into well-de?ned chiral OAM states and then to total angular momentum J-states. In addition, the energy scale of the band splitting changes from atomic SOC energy to electrostatic energy. To con?rm the validity of the model, we study OAM and spin structures of Au(111) system by using an effective Hamiltonian for the d-orbitals case. As for strong SOC regime, we choose Bi2Te2Se as a prototype system. We performed circular dichroism angle resolved photoemission spectroscopy experiments as well as ?rst-principles calculations. We ?nd that the effective model can explain various aspects of spin and OAM structures of the system.
    Physical Review B 09/2013; 88(20). DOI:10.1103/PhysRevB.88.205408 · 3.66 Impact Factor

Full-text (2 Sources)

Available from
May 29, 2014