We report the results of scanning tunneling microscopy experiments using iron-coated tungsten tips and current-carrying bismuth selenide (Bi$_2$Se$_3$) samples. Asymmetry in tunneling currents with respect to the change in the direction of bias currents through Bi$_2$Se$_3$ samples has been measured. It is argued that this asymmetry is the manifestation of surface spin-polarized electron accumulation caused by the 90$^\circ$ electron spin–momentum locking in the topologically protected surface current mode. It is demonstrated that the manifestation of surface spin-polarized electron accumulation is enhanced by tin doping of Bi$_2$Se$_3$ samples. Furthermore, we noted the appearance of spin-dependent density of states in current-carrying Bi$_2$Se$_3$ samples.

中文翻译：

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使用扫描隧道显微镜研究拓扑绝缘体中的表面自旋极化电子积累

我们报告了使用铁涂层钨尖端和载流硒化铋（Bi$_2$硒$_3$) 样品。隧道电流相对于通过 Bi 的偏置电流方向变化的不对称性$_2$硒$_3$样品进行了测量。有人认为，这种不对称性是由 90 度引起的表面自旋极化电子积累的表现。$^\circ$拓扑保护表面电流模式下的电子自旋动量锁定。结果表明，Bi的锡掺杂增强了表面自旋极化电子积累的表现$_2$硒$_3$样品。此外，我们注意到在载流 Bi 中出现了与自旋相关的态密度$_2$硒$_3$ 样品。