Price Christopher C, Frey Nathan C, Jariwala Deep, Shenoy Vivek B
Department of Materials Science and Engineering , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States.
Department of Electrical and Systems Engineering , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States.
ACS Nano. 2019 Jul 23;13(7):8303-8311. doi: 10.1021/acsnano.9b03716. Epub 2019 Jun 26.
Achieving robust, localized quantum states in two-dimensional (2D) materials like graphene is desirable for optoelectronics and quantum information yet challenging due to the difficulties in confining Dirac fermions. Traditional colloidal nanoparticle and epitaxially grown quantum dots are also impractical for solid-state devices, due to either complex surface chemistry, unreliable spatial positioning, or lack of electrical and optical access. In this work, we design and optimize nanoscale monolayer transition-metal dichalcogenide (TMD) heterostructures to natively host massive Dirac fermion bound states. We develop an integrated multiscale approach to translate first-principles electronic structure to higher length scales, where we apply a continuum model to consider arbitrary 2D quantum dot geometries and sizes. Focusing on a model system of an MoS quantum dot in a WS matrix (MoS/WS), we find discrete bound states in triangular dots with side lengths up to 20 nm. We propose figures of merit that, when optimized for, result in heterostructure configurations engineered for maximally isolated bound states at room temperature. These design principles apply to the entire family of semiconducting TMD materials, and we predict 6.5 nm MoS/WS (quantum dot/matrix) triangular dots and 4.5 nm MoSe/WSe triangular dots as ideal systems for confining massive Dirac fermions.
在诸如石墨烯等二维（2D）材料中实现稳健的局域量子态，对于光电子学和量子信息而言是很有必要的，但由于在限制狄拉克费米子方面存在困难，因此颇具挑战性。传统的胶体纳米颗粒和外延生长的量子点对于固态器件来说也不实用，这是因为它们要么具有复杂的表面化学性质、空间定位不可靠，要么缺乏电学和光学通道。在这项工作中，我们设计并优化了纳米级单层过渡金属二硫属化物（TMD）异质结构，以原生方式容纳大量狄拉克费米子束缚态。我们开发了一种集成多尺度方法，将第一性原理电子结构转换到更高的长度尺度，在此我们应用连续介质模型来考虑任意二维量子点的几何形状和尺寸。聚焦于WS矩阵（MoS/WS）中MoS量子点的模型系统，我们在边长高达20 nm的三角形量子点中发现了离散束缚态。我们提出了品质因数，当对其进行优化时，会得到在室温下为最大程度隔离束缚态而设计的异质结构配置。这些设计原则适用于整个半导体TMD材料家族，并且我们预测6.5 nm的MoS/WS（量子点/矩阵）三角形量子点和4.5 nm的MoSe/WSe三角形量子点是限制大量狄拉克费米子的理想系统。
