Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA.
Joint Institute for Advanced Materials at The University of Tennessee, Knoxville, Tennessee 37996, USA.
Nat Commun. 2017 Mar 7;8:14721. doi: 10.1038/ncomms14721.
Semiconductor surfaces and ultrathin interfaces exhibit an interesting variety of two-dimensional quantum matter phases, such as charge density waves, spin density waves and superconducting condensates. Yet, the electronic properties of these broken symmetry phases are extremely difficult to control due to the inherent difficulty of doping a strictly two-dimensional material without introducing chemical disorder. Here we successfully exploit a modulation doping scheme to uncover, in conjunction with a scanning tunnelling microscope tip-assist, a hidden equilibrium phase in a hole-doped bilayer of Sn on Si(111). This new phase is intrinsically phase separated into insulating domains with polar and nonpolar symmetries. Its formation involves a spontaneous symmetry breaking process that appears to be electronically driven, notwithstanding the lack of metallicity in this system. This modulation doping approach allows access to novel phases of matter, promising new avenues for exploring competing quantum matter phases on a silicon platform.
半导体表面和超薄界面呈现出各种有趣的二维量子物质相，如电荷密度波、自旋密度波和超导凝聚态。然而，由于在不引入化学无序的情况下对严格的二维材料进行掺杂非常困难，这些对称性破缺相的电子性质极难控制。在这里，我们成功地利用调制掺杂方案，结合扫描隧道显微镜针尖辅助，揭示了在 Si(111)上的 Sn 双层中掺杂空穴时的一个隐藏的平衡相。这个新相本质上是由具有极性和非极性对称性的绝缘畴分离而成。它的形成涉及一个自发的对称破缺过程，尽管这个系统中没有金属性，但它似乎是由电子驱动的。这种调制掺杂方法为探索硅平台上的竞争量子物质相提供了新的途径。
