| 1. |
- Annese, Emilia, et al.
(författare)
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Nonvortical Rashba Spin Structure on a Surface with C1h Symmetry
- 2016
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Ingår i: Physical Review Letters. - 0031-9007. ; 117:1
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Tidskriftsartikel (refereegranskat)abstract
- A totally anisotropic peculiar Rashba-Bychkov (RB) splitting of electronic bands was found on the Tl/Si(110)-(1×1) surface with C1h symmetry by angle- and spin-resolved photoelectron spectroscopy and first-principles theoretical calculation. The constant energy contour of the upper branch of the RB split band has a warped elliptical shape centered at a k point located between Γ and the edge of the surface Brillouin zone, i.e., at a point without time-reversal symmetry. The spin-polarization vector of this state is in-plane and points almost the same direction along the whole elliptic contour. This novel nonvortical RB spin structure is confirmed as a general phenomenon originating from the C1h symmetry of the surface.
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| 2. |
- Cossu, Fabrizio, et al.
(författare)
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Unveiling hidden charge density waves in single-layer NbSe2 by impurities
- 2018
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Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 98:19
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Tidskriftsartikel (refereegranskat)abstract
- We employ ab initio calculations to investigate the charge density waves in single-layer NbSe2, and we explore how they are affected by transition metal atoms. Our calculations reproduce the observed orthorhombic phase in single-layer NbSe2 in the clean limit, establishing the energy order between three different distorted structures, two consisting of triangular Nb-Nb clusters and a third, energetically unfavored, consisting of hexagonal Nb-Nb clusters. Such energy order, in agreement with known experimental work, is reversed by the adsorption of Co and Mn, which favor the formation of hexagonal Nb-Nb clusters; this CDW structure is indeed allowed from a symmetry point of view but hidden in pure single layers because it is at a higher energy. The other adsorbates, K and Ga, still favor one of the triangular Nb-Nb cluster, while suppressing the other. We report how the energy difference between such distorted structure varies with these adsorbates. Furthermore, transition metals induce magnetism and favor the reduction of the symmetry of the charge density distribution.
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| 3. |
- Sakamoto, Kazuyuki, et al.
(författare)
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Determination of the bonding configuration of the metastable molecular oxygen adsorbed on a Si(111)-(7×7) surface
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 65:20
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Tidskriftsartikel (refereegranskat)abstract
- The initial adsorption stage of oxygen on a Si(111)-(7×7) surface has been investigated using real time high-resolution core-level measurements at 100 K. Among the six O 1s components observed on an O2 exposed Si(111) surface, the three components, whose intensities saturate at the same dosage, have the same lifetime. These results lead to a conclusion that three oxygen atoms with different chemical environments compose the metastable species. Based on a comparison with our calculated O 1s binding energies, we have determined the bonding configuration of the metastable oxygen.
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| 4. |
- Sakamoto, Kazuyuki, et al.
(författare)
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Symmetry induced peculiar Rashba effect on thallium adsorbed Si(111) surfaces
- 2015
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier. - 0368-2048 .- 1873-2526. ; 201, s. 88-91
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Tidskriftsartikel (refereegranskat)abstract
- The geometric symmetry of the surface plays an important role for the spin-orbit-induced spin texture of two-dimensional electronic states. This article reviews the peculiar Rashba spins induced by a C-3 symmetry, including the completely spin polarized surface states with the polarization vector oriented perpendicular to the surface, i.e. a direction that is not expected in a typical Rashba system. This review also describes that this peculiar Rashba situation has possibility to suppress backscattering and therefore to greatly improve the efficiency of spin transport, which is an essential issue in the development of high-performance semiconductor spintronic devices. (C) 2014 Elsevier B.V. All rights reserved.
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| 5. |
- Sakamoto, Kazuyuki, et al.
(författare)
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Valley spin polarization by using the extraordinary Rashba effect on silicon
- 2013
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Ingår i: Nature Communications. - : Nature Publishing Group: Nature Communications. - 2041-1723. ; 4:2073
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Tidskriftsartikel (refereegranskat)abstract
- The addition of the valley degree of freedom to a two-dimensional spin-polarized electronic system provides the opportunity to multiply the functionality of next-generation devices. So far, however, such devices have not been realized due to the difficulty to polarize the valleys, which is an indispensable step to activate this degree of freedom. Here we show the formation of 100% spin-polarized valleys by a simple and easy way using the Rashba effect on a system with C-3 symmetry. This polarization, which is much higher than those in ordinary Rashba systems, results in the valleys acting as filters that can suppress the backscattering of spin-charge. The present system is formed on a silicon substrate, and therefore opens a new avenue towards the realization of silicon spintronic devices with high efficiency.
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