Proximate Two-Dimensional Electron and Hole Gases in Ambipolar Cuprates

非技术描述：控制原子如何相互作用的定律与我们日常生活中的规律有很大不同，比如棒球如何在空气中飞行，海浪如何移动和相互作用。对于原子，我们对粒子和波的概念融合在一起，并用量子力学来描述它们的相互作用。虽然通常被归入原子尺度，但只有用量子力学才能解释的行为，可以从微观世界超越到宏观世界，并产生一些壮观的效果。例子包括超导、超流和相干物质波。这项工作的长期目标是在一个具有实际意义的温度下，实现固体中运动的相反电荷对的相干波。相反电荷对的相干波在其中运动的物质可以为社会提供对下一代电子有用的行为。为此，PI将逐个原子地创建包含铜和氧的目标结构，并精确控制它们的排列和原子之间的间距。这项研究的更广泛影响包括培训本科生和研究生使用已知的最复杂的技术之一来创造新材料，通过逐个原子控制它们的组装方式。技术细节：该项目的技术目标是生长具有可调空穴或电子移动载流子浓度的新的铜氧化物超导体。获得一种可以掺杂空穴或电子的超导体，可以突然从空穴掺杂到电子掺杂，这是合成近二维电子液体和二维空穴液体的重要一步。这种方法的一个关键优点是，产生的激子系统处于其基态；它不依赖于光激发来产生它，不受复合的影响，因此，原则上可以获得更高的激子载流子浓度，这是一种完全未知的物质状态，在这种状态下，预计会有不寻常的行为(例如玻色凝聚)。虽然已知氧化物系统既可以支持二维电子液体，也可以支持二维空穴液体，但只有少数氧化物中的同一母相可以以双极方式高度掺杂。其中最突出的是SrCuO2，即所谓的“无限层”铜酸盐，它是所有高转变温度(高TC)铜酸盐超导体的母体结构。这项研究的更广泛影响包括培训学生使用最复杂的合成技术之一，分子束外延以创造原子水平控制组成原子的氧化物材料而闻名。

NON-TECHNICAL DESCRIPTION: The laws that govern how atoms interact differ significantly from what we are used to in everyday life such as how baseballs fly through the air or ocean waves move and interact with each other. For atoms, our notions of particles and waves merge together and quantum mechanics are used to describe their interactions. Although commonly relegated to atomic scales, behavior that is only explainable with the use of quantum mechanics can transcend from the microscopic to the macroscopic world and produce some spectacular effects. Examples include superconductivity, superfluidity, and coherent matter waves. The long-term goal of this work is to achieve coherent waves of moving pairs of opposite charges in a solid at a temperature where they could be of practical importance. Matter within which coherent waves of opposite charge pairs move could provide society with behaviors useful for the next generation of electronics. Toward this end, the PI will create targeted structures containing copper and oxygen atom-by-atom with precise control of their arrangement and the spacing between the atoms. The broader impact of this research includes the training of undergraduate and graduate students to use one of the most sophisticated techniques known for creating new materials with atom-by-atom control of how they are assembled.TECHNICAL DETAILS: The technical objective of this project is to grow new copper-oxide-based superconductors with tunable hole or electron mobile carrier concentrations. Achieving a superconductor that can be doped with holes or electrons in a way that can switch abruptly from hole to electron doping is an important step on the path to synthesizing proximal two-dimensional electron liquids and two-dimensional hole liquids. A key advantage of this approach is that the resulting excitonic system created is in its ground state; it does not rely on optical excitation for its creation, is not subject to recombination, and can thus, in principle, access much higher exciton carrier concentrations, a completely uncharted state of matter where unusual behavior (e.g., Bose condensation) is expected. Although oxide systems are known that can support either two-dimensional electron liquids or two-dimensional hole liquids, there are only a few oxides in which the same parent phase can be highly doped in an ambipolar manner. A standout among these is SrCuO2, the so-called "infinite-layer" cuprate, which is the parent structure of all high transition temperature (high Tc) cuprate superconductors. The broader impact of this research includes the training of students to use one of the most sophisticated synthesis techniques, molecular-beam epitaxy known for creating oxide materials with atomic-level control of the constituent atoms.