Revealing the Hidden Spin-Polarized Bands in a Superconducting Tl Bilayer Crystal

The interplay of spin-orbit coupling and crystal symmetry can generate spin-polarized bands in materials only a few atomic layers thick, potentially leading to unprecedented physical properties. In the case of bilayer materials with global inversion symmetry, locally broken inversion symmetry can generate degenerate spin-polarized bands, in which the spins in each layer are oppositely polarized. Here, we demonstrate that the hidden spins in a Tl bilayer crystal are revealed by growing it on Ag(111) of sizable lattice mismatch, together with the appearance of a remarkable phenomenon unique to centrosymmetric hidden-spin bilayer crystals: a novel band splitting in both spin and space. The key to success in observing this novel splitting is that the interaction at the interface has just the right strength: it does not destroy the original wave functions of the Tl bilayer but is strong enough to induce an energy separation

Creation of a <i>p</i>-type TlBiSe2 using photo-induced doping

Owing to the location of the Dirac point, which is around the center of its wide bulk band gap, TlBiSe2 would be one of the most promising topological insulators for spintronics devices material. However, like many other topological insulators, defects, such as vacancy formed during the crystal growth, dope electrons into TlBiSe2 and make its bulk metallic. Here, we show the achievement of bulk insulating both n-type and p-type TlBiSe2 by photo-induced doping, a method carried out by a combination of photo-irradiation and H2O adsorption. We also show that the main trigger of this photo-induced doping is the excitation of the outermost d core level of the chalcogen atoms of the topmost layer as in the case of Bi2X3, where X = Se or Te.11Nsciescopu

Robots and Machines

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