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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.


py-projected spectral weight distribution.(A) Experimental geometry for our measurements and (B to D) resulting CESs measured using s-polarized light to probe the py orbital character at 200 meV above, exactly at, and at 100 meV below the Dirac point (ED) formed by the crossing of the two spin-split branches of the lowest subband. On-resonance measurements (hν = 28 eV) with the scattering plane aligned to (B) Γ–M and (C) Γ–K, and (D) off-resonance (hν = 30 eV, scattering plane along Γ–K) measurements show pronounced angular variations in spectral weight, characteristic of strongly momentum-dependent orbital textures.
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Figure 3: py-projected spectral weight distribution.(A) Experimental geometry for our measurements and (B to D) resulting CESs measured using s-polarized light to probe the py orbital character at 200 meV above, exactly at, and at 100 meV below the Dirac point (ED) formed by the crossing of the two spin-split branches of the lowest subband. On-resonance measurements (hν = 28 eV) with the scattering plane aligned to (B) Γ–M and (C) Γ–K, and (D) off-resonance (hν = 30 eV, scattering plane along Γ–K) measurements show pronounced angular variations in spectral weight, characteristic of strongly momentum-dependent orbital textures.

Mentions: The resulting measurements of the dispersion reveal pronounced momentum-dependent spectral weight variations (Fig. 2C). We focus on the first subband (SB1), which is most clearly visible across our measurements. Measurements using p-polarized light yield stronger spectral weight for the inner branch of this subband, whereas the outer branch is significantly more pronounced when probed using s-polarization. Selection rules (19) dictate that, of the p orbitals, the former measurement should be sensitive to pz- and px-derived orbital character, whereas the transition matrix element is only nonvanishing for photoemission from py orbitals in the latter case (our measurement geometry is shown in Fig. 3A). The asymmetric spectral weight distributions within and between these measurements immediately establish that the two spin-split branches of the dispersion host a markedly different orbital makeup. Moreover, when measuring with a photon energy only 2 eV higher (Fig. 2D), we find an almost complete reversal of these matrix element variations, with greater spectral weight for the inner branch of the lowest subband when measuring using s-polarized light. No longer on resonance, these measurements will not a priori be dominated by the Bi-derived spectral weight, and we therefore conclude that the orbital textures of the Rashba-split states are also strongly dependent on their underlying atomic character, as discussed in detail below.


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)

py-projected spectral weight distribution.(A) Experimental geometry for our measurements and (B to D) resulting CESs measured using s-polarized light to probe the py orbital character at 200 meV above, exactly at, and at 100 meV below the Dirac point (ED) formed by the crossing of the two spin-split branches of the lowest subband. On-resonance measurements (hν = 28 eV) with the scattering plane aligned to (B) Γ–M and (C) Γ–K, and (D) off-resonance (hν = 30 eV, scattering plane along Γ–K) measurements show pronounced angular variations in spectral weight, characteristic of strongly momentum-dependent orbital textures.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: py-projected spectral weight distribution.(A) Experimental geometry for our measurements and (B to D) resulting CESs measured using s-polarized light to probe the py orbital character at 200 meV above, exactly at, and at 100 meV below the Dirac point (ED) formed by the crossing of the two spin-split branches of the lowest subband. On-resonance measurements (hν = 28 eV) with the scattering plane aligned to (B) Γ–M and (C) Γ–K, and (D) off-resonance (hν = 30 eV, scattering plane along Γ–K) measurements show pronounced angular variations in spectral weight, characteristic of strongly momentum-dependent orbital textures.
Mentions: The resulting measurements of the dispersion reveal pronounced momentum-dependent spectral weight variations (Fig. 2C). We focus on the first subband (SB1), which is most clearly visible across our measurements. Measurements using p-polarized light yield stronger spectral weight for the inner branch of this subband, whereas the outer branch is significantly more pronounced when probed using s-polarization. Selection rules (19) dictate that, of the p orbitals, the former measurement should be sensitive to pz- and px-derived orbital character, whereas the transition matrix element is only nonvanishing for photoemission from py orbitals in the latter case (our measurement geometry is shown in Fig. 3A). The asymmetric spectral weight distributions within and between these measurements immediately establish that the two spin-split branches of the dispersion host a markedly different orbital makeup. Moreover, when measuring with a photon energy only 2 eV higher (Fig. 2D), we find an almost complete reversal of these matrix element variations, with greater spectral weight for the inner branch of the lowest subband when measuring using s-polarized light. No longer on resonance, these measurements will not a priori be dominated by the Bi-derived spectral weight, and we therefore conclude that the orbital textures of the Rashba-split states are also strongly dependent on their underlying atomic character, as discussed in detail below.

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.