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Hierarchical spin-orbital polarization of a giant Rashba system.

Bawden L, Riley JM, Kim CH, Sankar R, Monkman EJ, Shai DE, Wei HI, Lochocki EB, Wells JW, Meevasana W, Kim TK, Hoesch M, Ohtsubo Y, Le Fèvre P, Fennie CJ, Shen KM, Chou F, King PD - Sci Adv (2015)

Bottom Line: The Rashba effect is one of the most striking manifestations of spin-orbit coupling in solids and provides a cornerstone for the burgeoning field of semiconductor spintronics.Combining polarization-dependent and resonant angle-resolved photoemission measurements with density functional theory calculations, we show that the two "spin-split" branches of the model giant Rashba system BiTeI additionally develop disparate orbital textures, each of which is coupled to a distinct spin configuration.This necessitates a reinterpretation of spin splitting in Rashba-like systems and opens new possibilities for controlling spin polarization through the orbital sector.

View Article: PubMed Central - PubMed

Affiliation: SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK.

ABSTRACT
The Rashba effect is one of the most striking manifestations of spin-orbit coupling in solids and provides a cornerstone for the burgeoning field of semiconductor spintronics. It is typically assumed to manifest as a momentum-dependent splitting of a single initially spin-degenerate band into two branches with opposite spin polarization. Combining polarization-dependent and resonant angle-resolved photoemission measurements with density functional theory calculations, we show that the two "spin-split" branches of the model giant Rashba system BiTeI additionally develop disparate orbital textures, each of which is coupled to a distinct spin configuration. This necessitates a reinterpretation of spin splitting in Rashba-like systems and opens new possibilities for controlling spin polarization through the orbital sector.

No MeSH data available.


Hierarchy of atomic, spin, and orbital coupling in BiTeI.(A) Schematic representation of disparate in-plane orbital textures uncovered for the inner and outer “spin-split” branches of a model Rashba system. (B to D) Corresponding spin textures calculated from DFT for Bi (B) px, (C) py, and (D) pz projections of CESs 200 meV above the Dirac point. The in-plane spin texture is shown by arrows, and the out-of-plane by the background color, both in units of ℏ/2. (E) Schematic of the in-plane spin textures coupled to the net in-plane and out-of-plane orbital textures. (F) Circular dichroism measurements performed on-resonance (hν = 28 eV, CES at ED + 200 meV), revealing a significant sixfold modulation for the outer band indicative of pronounced out-of-plane spin canting.
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Figure 5: Hierarchy of atomic, spin, and orbital coupling in BiTeI.(A) Schematic representation of disparate in-plane orbital textures uncovered for the inner and outer “spin-split” branches of a model Rashba system. (B to D) Corresponding spin textures calculated from DFT for Bi (B) px, (C) py, and (D) pz projections of CESs 200 meV above the Dirac point. The in-plane spin texture is shown by arrows, and the out-of-plane by the background color, both in units of ℏ/2. (E) Schematic of the in-plane spin textures coupled to the net in-plane and out-of-plane orbital textures. (F) Circular dichroism measurements performed on-resonance (hν = 28 eV, CES at ED + 200 meV), revealing a significant sixfold modulation for the outer band indicative of pronounced out-of-plane spin canting.

Mentions: Together, these measurements and calculations reveal that spin-orbit coupling induces a complex atomic and momentum-dependent hierarchy of orbitally polarized components of the underlying electronic structure in BiTeI, summarized schematically in Fig. 5. Our calculations additionally reveal how each orbital component is, in turn, coupled to a disparate spin texture. We illustrate this for the Bi-derived states in Fig. 5 (B to D); the Te-derived component is additionally shown in fig. S2. The in-plane spin-texture 〈Sx,y〉 projected onto Bi pz orbitals yields a conventional counter-rotating chiral spin texture of neighboring CESs at energies above the Dirac point, characteristic of classic Rashba systems (2, 3) and indeed experimentally observed for BiTeI (13, 16). In contrast, the spin texture is significantly more complex for the px and py orbital projection, with the in-plane spin component switching between tangential and radial around the CES. This results from a coupling of the spin to the characteristic orbital textures, which is similar to that recently found for topological surface states (25–27).


Hierarchical spin-orbital polarization of a giant Rashba system.

Bawden L, Riley JM, Kim CH, Sankar R, Monkman EJ, Shai DE, Wei HI, Lochocki EB, Wells JW, Meevasana W, Kim TK, Hoesch M, Ohtsubo Y, Le Fèvre P, Fennie CJ, Shen KM, Chou F, King PD - Sci Adv (2015)

Hierarchy of atomic, spin, and orbital coupling in BiTeI.(A) Schematic representation of disparate in-plane orbital textures uncovered for the inner and outer “spin-split” branches of a model Rashba system. (B to D) Corresponding spin textures calculated from DFT for Bi (B) px, (C) py, and (D) pz projections of CESs 200 meV above the Dirac point. The in-plane spin texture is shown by arrows, and the out-of-plane by the background color, both in units of ℏ/2. (E) Schematic of the in-plane spin textures coupled to the net in-plane and out-of-plane orbital textures. (F) Circular dichroism measurements performed on-resonance (hν = 28 eV, CES at ED + 200 meV), revealing a significant sixfold modulation for the outer band indicative of pronounced out-of-plane spin canting.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643772&req=5

Figure 5: Hierarchy of atomic, spin, and orbital coupling in BiTeI.(A) Schematic representation of disparate in-plane orbital textures uncovered for the inner and outer “spin-split” branches of a model Rashba system. (B to D) Corresponding spin textures calculated from DFT for Bi (B) px, (C) py, and (D) pz projections of CESs 200 meV above the Dirac point. The in-plane spin texture is shown by arrows, and the out-of-plane by the background color, both in units of ℏ/2. (E) Schematic of the in-plane spin textures coupled to the net in-plane and out-of-plane orbital textures. (F) Circular dichroism measurements performed on-resonance (hν = 28 eV, CES at ED + 200 meV), revealing a significant sixfold modulation for the outer band indicative of pronounced out-of-plane spin canting.
Mentions: Together, these measurements and calculations reveal that spin-orbit coupling induces a complex atomic and momentum-dependent hierarchy of orbitally polarized components of the underlying electronic structure in BiTeI, summarized schematically in Fig. 5. Our calculations additionally reveal how each orbital component is, in turn, coupled to a disparate spin texture. We illustrate this for the Bi-derived states in Fig. 5 (B to D); the Te-derived component is additionally shown in fig. S2. The in-plane spin-texture 〈Sx,y〉 projected onto Bi pz orbitals yields a conventional counter-rotating chiral spin texture of neighboring CESs at energies above the Dirac point, characteristic of classic Rashba systems (2, 3) and indeed experimentally observed for BiTeI (13, 16). In contrast, the spin texture is significantly more complex for the px and py orbital projection, with the in-plane spin component switching between tangential and radial around the CES. This results from a coupling of the spin to the characteristic orbital textures, which is similar to that recently found for topological surface states (25–27).

Bottom Line: The Rashba effect is one of the most striking manifestations of spin-orbit coupling in solids and provides a cornerstone for the burgeoning field of semiconductor spintronics.Combining polarization-dependent and resonant angle-resolved photoemission measurements with density functional theory calculations, we show that the two "spin-split" branches of the model giant Rashba system BiTeI additionally develop disparate orbital textures, each of which is coupled to a distinct spin configuration.This necessitates a reinterpretation of spin splitting in Rashba-like systems and opens new possibilities for controlling spin polarization through the orbital sector.

View Article: PubMed Central - PubMed

Affiliation: SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife KY16 9SS, UK.

ABSTRACT
The Rashba effect is one of the most striking manifestations of spin-orbit coupling in solids and provides a cornerstone for the burgeoning field of semiconductor spintronics. It is typically assumed to manifest as a momentum-dependent splitting of a single initially spin-degenerate band into two branches with opposite spin polarization. Combining polarization-dependent and resonant angle-resolved photoemission measurements with density functional theory calculations, we show that the two "spin-split" branches of the model giant Rashba system BiTeI additionally develop disparate orbital textures, each of which is coupled to a distinct spin configuration. This necessitates a reinterpretation of spin splitting in Rashba-like systems and opens new possibilities for controlling spin polarization through the orbital sector.

No MeSH data available.