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.
Using angle-resolved photoelectron spectroscopy we investigate the surface electronic structure of the threedimensional topological insulator (TI) Sb2Te3(0001). Our data show the presence of a topological surface state in the bulk energy gap with the Dirac-point located above the Fermi level. The adsorption of Cs-atoms on Sb2Te3(0001) gives rise to a downward energy shift of the electronic valence band states which saturates at a value of ∼200 meV. For the saturation coverage the Dirac-point of the linearly dispersive surface state resides in close proximity to the Fermi level. The electronic structure of the Cs/Sb2Te3 interface therefore considerably deviates from previously studied metal-TI interfaces based on the isostructural compound Bi2Se3 which points to the importance of atomic composition in these hetero systems.Three-dimensional topological insulators (TIs) are currently generating widespread scientific interest in the condensed matter physics community as the distinct topology of their bulk band structure provokes the existence of robust metallic surface states with unique physical properties.1,2 The surface states locally span the global energy gap in the electronic excitation spectrum of the bulk material and their existence is protected by time-reversal symmetry.3,4 A salient feature of topological surface states (TSSs) lies in their characteristic spin structure introduced by spin-orbit coupling which locks the spin to the direction perpendicular to the wave vector.5 As a consequence of this spin structure the backscattering of the surface state electrons from non-magnetic impurities is strongly suppressed.6 Currently, most research on TIs is devoted to the chalcogenide semiconductors Bi 2 Se 3 7,8 and Bi 2 Te 3 8,9 , related ternary compounds 10,11 as well as to HgTe quantum wells. 12 The TSSs of these materials show a particularly simple dispersion consisting of a single spin-polarized Dirac-cone.The experimental realization of the most appealing properties of TSSs that have been predicted so far will require interface structures between TIs and metal films. This holds for example for the topological magnetoelectric effect at the interface of a TI and a ferromagnet 13,14 as well as for Majorana fermions at the interface of a TI and a superconductor. 15 It is therefore important to investigate the influence of metallic adlayers on the electronic structure of TI surfaces. Surfacesensitive spectroscopic techniques and in particular angleresolved photoelectron spectroscopy (ARPES), which also played a key role in the discovery of TIs 1 , are suitable methods to study modifications in the electronic structure during the formation of interfaces 16 . Indeed, great experimental effort on the basis of ARPES is currently directed towards an improved understanding of the influence of adsorbates on the electronic structure of TI surfaces. [17][18][19][20][21][22][23] However, most of these works have focused on the TI surface Bi 2 Se 3 (0001). It therefore appears essential to expand the present investigati...
A totally anisotropic peculiar Rashba-Bychkov (RB) splitting of electronic bands was found on the Tl/Si(110)-(1×1) surface with C_{1h} 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[over ¯] 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 C_{1h} symmetry of the surface.
Spatially controlling the Fermi level of topological insulators and keeping their electronic states stable are indispensable processes to put this material into practical use for semiconductor spintronics devices. So far, however, such a method has not been established yet. Here we show a novel method for doping a hole into n-type topological insulators Bi 2 X 3 (X= Se, Te) that overcomes the shortcomings of the previous reported methods. The key of this doping is to adsorb H 2 O on Bi 2 X 3 decorated with a small amount of carbon, and its trigger is the irradiation of a photon with sufficient energy to excite the core electrons of the outermost layer atoms. This method allows controlling the doping amount by the irradiation time and acts as photolithography. Such a tunable doping makes it possible to design the electronic states at the nanometer scale and, thus, paves a promising avenue toward the realization of novel spintronics devices based on topological insulators.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.