SGER: Controlling the Dispersion of Newly Discovered Acoustic Surface Plasmons

* 非技术摘要 * 最近有一个惊人的发现，铍（一种金属）表面上的电子的行为非常像湖面上的波浪。 这一观察结果与现有的物理学相矛盾，该物理学认为，金属表面上的电子只有在能量高于一定值（通常为几个电子伏（eV））时才能被集体激发或形成波。 根据新发现的现象，电子可以在更宽的范围内集体激发，从低得多的能量开始，只有1/1000 eV，并持续到许多eV。 这种新的激发被称为声表面等离子体（ASP）。 这项探索性研究小额赠款（SGER）支持一个项目，该项目将（i）使用复杂的方法在铜和银等技术重要的表面上测试这种新现象的普遍性。 (ii)它还将测试我们对这种现象所呈现的新物理学的理解，通过在原子水平上诱导受控的表面改性并测量它们对ASP的影响。 这些实验时间紧迫，因为有关铍的结果已引起全世界的注意，而且需要确认原始结果的普遍性。该研究预计将对表面化学反应，纳米光学和等离子体共振显微镜的基本理解产生深远的影响，并具有潜在的应用，例如在单个电路上直接集成光学和电子器件。该项目的合作性质向学生和博士后介绍了各种国际研究实验室，实验技术和理论方法。技术摘要 * 该SGER支持寻求对最近发现的Be（0001）上的声表面等离子体（ASP）的新物理学提供实质性见解的研究，该声表面等离子体是与金属表面结合的电子的低能集体激发。 它的智力价值在于它挑战了我们对集体表面激发的基本理解。 该项目的第一部分将尝试直接观察Cu（111）和Ag（111）上的ASP，从而显示这种新现象的一般特征。 为此，电子能量损失谱测量将在为这些测量提供最佳条件的协作设施中进行。 该项目的第二部分将着眼于表面改性对ASP分散的影响。 根据不断发展的理解，ASP的存在是因为底层体电子对表面电子的非局域屏蔽。因此，通过标准表面科学技术对表面状态分散体的改性预计会改变ASP本身。 考虑到这一点，ASP分散在两个已知的氢诱导的Be（0001）表面的重建将被测量和第一性原理计算进行比较。 这些实验时间紧迫，因为有关铍的结果已引起全世界的注意，而且需要确认原始结果的普遍性。该研究预计将对表面化学反应，纳米光学和等离子体共振显微镜的基本理解产生深远的影响，并具有潜在的应用，例如在单个电路上直接集成光学和电子器件。该项目的合作性质向学生和博士后介绍了各种国际研究实验室，实验技术和理论方法。

*****NON-TECHNICAL ABSTRACT****Recently a startling discovery was made, electrons on beryllium (a metal) surfaces behave very much like waves on the surface of a lake. This observation contradicts established physics, which states that electrons on metal surfaces can only become collectively excited, or form a wave, if their energy lies above a certain value, generally of a few electron volts (eV). In the light of the newly discovered phenomenon, electrons can be collectively excited over a broader range starting at a much lower energy, a few 1/1000 of an eV, and continuing up to many eV. This novel excitation is called Acoustic Surface Plasmon (ASP). This Small Grant for Exploratory Research (SGER) supports a project that will (i) test the generality of this new phenomenon on technologically important surfaces such as copper and silver using sophisticated methods. (ii) It will also test our understanding of the new Physics presented by this phenomenon by inducing controlled surface modifications at the atomic level and measuring their effects on the ASP. The experiments are time-urgent since the results on beryllium have attracted worldwide attention and there is a need to confirm the generality of the original results. The research is expected to have a deep impact on the fundamental understanding of chemical reactions on surfaces, nano-optics, and plasmon resonant microscopy, with potential applications such as the direct integration of optical and electronic devices on a single circuit. The collaborative nature of this project introduces students and post-docs to various international research labs, experimental techniques and theoretical approaches.*****TECHNICAL ABSTRACT****This SGER supports research seeking to provide substantial insight into the new physics governing the recently discovered acoustic surface plasmon (ASP) on Be(0001), a low-energy collective excitation of the electrons bond to a metallic surface. Its intellectual merit lies in the fact that it challenges our basic understanding of collective surface excitations. The first part of the project will attempt a direct observation of the ASP on Cu(111) and Ag(111); thus showing the general character of this new phenomenon. To this effect, electron energy loss spectroscopy measurements will be performed at collaborative facilities that provide the best conditions for these measurements. The second part of the project will look at the influence of surface modifications on the ASP dispersion. According to developing understanding, the ASP exists because of the non-local screening of surface electrons by the underlying bulk electrons. Thus a modification of the surface state dispersion via standard surface science techniques is expected to alter the ASP itself. With this in mind, the ASP dispersion on the two known hydrogen induced reconstructions of the Be(0001) surface will be measured and compared with first-principles calculations. The experiments are time-urgent since the results on beryllium have attracted worldwide attention and there is a need to confirm the generality of the original results. The research is expected to have a deep impact on the fundamental understanding of chemical reactions on surfaces, nano-optics, and plasmon resonant microscopy, with potential applications such as the direct integration of optical and electronic devices on a single circuit. The collaborative nature of this project introduces students and post-docs to various international research labs, experimental techniques and theoretical approaches.