Imaging ambipolar two-dimensional carriers induced by the spontaneous electric polarization of a polar semiconductor BiTeI

Abstract

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.

arXiv comment23 pages, 8 figures

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• Uniaxial stress controlled anisotropic Rashba effects and carriers-based currents in BiTeI monolayer semiconductor
• Quasiparticle Interference in ZrSiS - Strongly Band-Selective Scattering Depending on Impurity Lattice Site
• Dispersing artifacts in FT-STS: a comparison of set point effects across acquisition modes
• Terahertz radiation by subpicosecond spin-polarized photocurrent originating from Dirac electrons in a Rashba-type polar semiconductor
• Quasiparticle interference in altermagnets
• Dirac Nodal Line and Rashba Splitting Surface States in Nonsymmorphic ZrGeTe
• Local and global patterns in quasiparticle interference: a reduced response function approach