Can spin-polarized photoemission measure spin properties in condensed matter?

Osterwalder, Jürg

doi:10.1088/0953-8984/24/17/171001

Cited by 12 publications

(10 citation statements)

References 19 publications

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“…Note in particular that, for each of 6 the subband branches, P x is compatible between all the data sets, which furthermore show systematically the opposite non-trivial spin-winding textures for the inner and outer light bands. These results prove that the helical spin structure, the giant spin splitting, and the subband spin polarization reported in this work, are all independent of the photon energy and polarization, hence inherent to the electronic structure of the 2DEG at the surface of SrTiO 3 [20]. On the other hand, contrary to P x , which does not change with photon energy or polarization, the out-of-plane component (P z ) of the spin polarization for the inner subband presents an anomaly (it gets inverted) at hν = 52 eV.…”

supporting

confidence: 80%

“…This means that the detected free electrons photo-emitted from the surface, whose spin polarization is well defined, have all spins essentially oriented along the same direction, tangential to the Fermi surface. These measured spin-splitting and polarizations are robust with respect to changes in photon energy and polarization (see below and Supplementary Note 3), supporting the interpretation as an intrinsic spin structure of the light subbands [20].…”

supporting

confidence: 67%

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Giant spin splitting of the two-dimensional electron gas at the surface of SrTiO3

et al. 2014

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1 Two-dimensional electron gases (2DEGs) forming at the interfaces of transition metal oxides [1][2][3] display a range of properties including tunable insulatorsuperconductor-metal transitions [4][5][6], large magnetoresistance [7], coexisting ferromagnetism and superconductivity [8, 9], and a spin splitting of a few meV [10,11]. Strontium titanate (SrTiO 3 ), the cornerstone of such oxide-based electronics, is a transparent, nonmagnetic, wide-band-gap insulator in the bulk, and has recently been found to host a surface 2DEG [12][13][14][15]. The most strongly confined carriers within this 2DEG comprise two sub-bands, separated by an energy gap of 90 meV and forming concentric circular Fermi surfaces [12,13,15].Using spin-and angle-resolved photoemission spectroscopy (SARPES), we show that the electron spins in these sub-bands have opposite chiralities. Although the Rashba effect might be expected to give rise to such spin textures, the giant splitting of almost 100 meV at the Fermi level is far larger than anticipated [16,17].Moreover, in contrast to a simple Rashba system, the spin-polarized sub-bands are non-degenerate at the Brillouin zone centre. This degeneracy can be lifted by time-reversal symmetry breaking, implying the possible existence of magnetic order. These results show that confined electronic states at oxide surfaces can be endowed with novel, non-trivial properties that are both theoretically challenging to anticipate and promising for technological applications.The 2DEG at the surface of SrTiO 3 , formed by confined electrons of the t 2g conduction band with Ti-3d character, is universal in the sense that its constituent subbands, their fillings, and their Fermi surfaces are independent of the bulk sample doping and of whether the surfaces are prepared by cleaving [12,13] or by etching and in situ annealing [15]. This 2DEG consists on two light electron subbands dispersing down to about −180 meV and, respectively, −90 meV below the Fermi level (E F ), producing concentric Fermi surfaces around the Brillouin zone center, and heavy shallow subbands dispersing down to about −40 meV, forming ellipsoidal Fermi surfaces [12,13,15].In fact, the 2DEG in SrTiO 3 has been associated with a band-bending of ∼ 300 meV at the surface of the material [12,13,15]. In such a quantum well profile, the most bound light subbands are tightly confined near the surface, while the less bound heavy subbands are more delocalized towards the bulk [12,15]. The present work focuses on resolving the spin 2 structure of the strongly two-dimensional light subbands, which are the most technologically relevant in terms of their carrier concentration and mobility.The surface band-bending of ∼ 300 meV amounts to an electric field F ∼ 100 MV/m confining the conduction electrons near the surface. In a simple approximation, this field will induce a so-called "Rashba splitting" of the spin states in each subband, with the largest splitting occurring for the most bound subbands. In an ideal surface, the corresponding momentum separat...

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confidence: 80%

supporting

confidence: 67%

Giant spin splitting of the two-dimensional electron gas at the surface of SrTiO3

et al. 2014

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“…Thus, the DA30-L spin spectrometer enables analysis of the 3D spin vector of photoelectrons emitted in the acceptance cone of (θ x × θ y ) = (30° × 24°) without sample rotation. Note, however, that, in general, the spin-polarization signal can be complicated by matrix element effects [161][162][163] . Thus, photon-energy-dependent and photon-polarizationdependent spin-resolved ARPES measurements are needed to check whether the spin signal is intrinsic to the magnetic moment of the photoelectrons 45,46 .…”

Section: Spin-resolved Arpesmentioning

confidence: 99%

Angle-resolved photoemission spectroscopy and its application to topological materials

2019

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“…The additional information on spin polarization can be obtained through spin-resolved ARPES (SARPES) [31,32,33] as has been shown for topological surface states in topological insulators [34,35,36]. There has been only a few SARPES studies on MX 2 [37,38,39] despite the large interest on the material class, mainly due to the difficulty in preparing large area samples suitable for measurements in ultra-high vacuum environment, as current SARPES setups at the synchrotron source are bound to large beam spot size to allow maximum photon flux.…”

Section: Introductionmentioning

confidence: 99%

Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films

Mo¹,

Hwang²,

Zhang³

et al. 2016

J. Phys.: Condens. Matter

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Abstract. MoSe 2 and WSe 2 with a few layer thickness possess non-trivial spin texture with sizable spin splitting due to the inversion symmetry breaking embedded in the crystal structure and strong spin-orbit coupling. We report spinresolved photoemission study of the MoSe 2 and WSe 2 thin film samples epitaxially grown on bilayer graphene substrate. We found spin polarization only in singleand tri-layer samples, but not in bi-layer sample, mostly along the out-of-plane direction of the sample surface. The measured spin polarization is found to be strongly dependent on the light polarization as well as the measurement geometry, which reveals intricate coupling between spin and orbital degrees of freedom in this material class.

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Can spin-polarized photoemission measure spin properties in condensed matter?

Cited by 12 publications

References 19 publications

Giant spin splitting of the two-dimensional electron gas at the surface of SrTiO3

Giant spin splitting of the two-dimensional electron gas at the surface of SrTiO3

Angle-resolved photoemission spectroscopy and its application to topological materials

Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films

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Can spin-polarized photoemission measure spin properties in condensed matter?

Cited by 12 publications

References 19 publications

Giant spin splitting of the two-dimensional electron gas at the surface of SrTiO3

Giant spin splitting of the two-dimensional electron gas at the surface of SrTiO3

Angle-resolved photoemission spectroscopy and its application to topological materials

Spin-resolved photoemission study of epitaxially grown MoSe2and WSe2thin films

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Spin-resolved photoemission study of epitaxially grown MoSe₂and WSe₂thin films