Imaging ambipolar two-dimensional carriers induced by the spontaneous electric polarization of a polar semiconductor BiTeI
Imaging ambipolar two-dimensional carriers induced by the spontaneous electric polarization of a polar semiconductor BiTeI
复制标题
DOI：
10.1103/physrevb.91.245312
复制
发表时间：
2015-06
影响因子：
3.7
通讯作者：
Y. Kohsaka;M. Kanou;H. Takagi;T. Hanaguri;T. Sasagawa
中科院分区：
文献类型：
--
作者：
Y. Kohsaka;M. Kanou;H. Takagi;T. Hanaguri;T. Sasagawa
二维（2D）移动的载流子是量子现象的源泉。在各种2D载流子系统中，如场效应晶体管和异质结构，极性材料具有独特的电势;体中的自发电极化可以在表面产生正和负的2D载流子。虽然几个实验表明双极载流子在极性半导体BiTeI的表面，其起源尚未被指定。在这里，我们提供了令人信服的实验证据表明，双极二维载流子在BiTeI的表面诱导的自发电极化。通过扫描隧道显微镜对电子驻波进行成像，我们发现在体相的极性方向对应的表面出现了具有Rashba型自旋分裂的正或负载流子。在表面的电子密度是恒定的，独立于那些在散装，证实了2D载流子的自发电极化诱导。我们还成功地图像，横向$p$-$n$结形成沿着边界的亚微米级领域与相反的极性方向。我们的研究提出了一种新的手段，赋予非易失性，自旋极化，双极二维载体，以及，没有精心制作，横向p$-$n$结的这些载体在原子尖锐的接口。
Two-dimensional (2D) mobile carriers are a wellspring of quantum phenomena. Among various 2D-carrier systems, such as field effect transistors and heterostructures, polar materials hold a unique potential; the spontaneous electric polarization in the bulk could generate positive and negative 2D carriers at the surface. Although several experiments have shown ambipolar carriers at the surface of a polar semiconductor BiTeI, their origin is yet to be specified. Here we provide compelling experimental evidences that the ambipolar 2D carriers at the surface of BiTeI are induced by the spontaneous electric polarization. By imaging electron standing waves with spectroscopic imaging scanning tunneling microscopy, we find that positive or negative carriers with Rashba-type spin splitting emerge at the surface correspondingly to the polar directions in the bulk. The electron densities at the surface are constant independently of those in the bulk, corroborating that the 2D carriers are induced by the spontaneous electric polarization. We also successfully image that lateral $p$-$n$ junctions are formed along the boundaries of submicron-scale domains with opposite polar directions. Our study presents a novel means to endow non-volatile, spin-polarized, and ambipolar 2D carriers as well as, without elaborate fabrication, lateral $p$-$n$ junctions of those carriers at atomically-sharp interfaces.