受压二维黑磷中的稳定和原始拓扑Dirac半金属相
Robust and Pristine Top ological Dirac Semimetal Phase in Pressured Two-Dimensional Black Phosphorous
摘要：
近年来，尽管人们在磷烯中寻找二维拓扑狄拉克半金属（2D TDSM），但仍然缺乏实验上有效的方法来激活这种相变，并且拓扑相位获取的基本机制仍然存在争议。在这里，从第一性原理计算结合带排序技术的基础上k.p理论，层压拓扑相图得到澄清的一些争议。我们表明，与外部电场，应变或吸附掺杂调谐相比，静水压力可以是一种实验上更可行的方式来激活拓扑相变的二维TDSM采集磷烯。更重要的是，由此产生的TDSM状态是一个原始的阶段，在费米能级上拥有一对受保护的狄拉克锥，与压力下的块状黑磷形成惊人的对比，在那里只能获得载流子混合的狄拉克态。我们证实，狄拉克点是强大的外部扰动下，只要滑翔平面对称性保持。我们的研究结果提供了一种手段，实现二维原始TDSM在一个更可实现的方式，这可能是至关重要的实现可控的TDSM态磷烯和相关的二维材料。
英文摘要：
Very recently, in spite of various efforts in searching for two dimensional topological Dirac semimetals (2D TDSMs) in phosphorene, there remains a lack of experimentally efficient way to activate such phase transition and the underlying mechanism for the topological phase acquisition is still controversial. Here, from first-principles calculations in combination with a band-sorting technique based on k.p theory, a layer-pressure topological phase diagram is obtained and some of the controversies are clarified. We demonstrate that, compared with tuning by external electric-fields, strain or doping by adsorption, hydrostatic pressure can be an experimentally more feasible way to activate the topological phase transition for 2D TDSM acquisition in phosphorene. More importantly, the resultant TDSM state is a pristine phase possessing a single pair of symmetry-protected Dirac cones right at the Fermi level, in startling contrast to the pressured bulk black phosphorous where only a carrier-mixed Dirac state can be obtained. We corroborate that the Dirac points are robust under external perturbation as long as the glide-plane symmetry preserves. Our findings provide a means to realize 2D pristine TDSM in a more achievable manner, which could be crucial in the realization of controllable TDSM states in phosphorene and related 2D materials.
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