Controlling Emergent Orders in Quantum Materials

普通金属和绝缘体的性质已经被很好地理解，电子结构的数值计算通常提供惊人的精度，使设计具有特定性质的材料的计算方法成为可能。这种理解水平在半导体电子学的发展中起了重要作用。量子材料表现出广泛的理想特性，使新的功能，但这些通常是意想不到的，他们的属性无法预测。量子材料令人惊讶的特性的主要例子是巨大的磁阻和高温超导性。高温超导发生在比传统超导体高出近十倍的温度下（除了在压力下），而巨磁阻表现出比巨磁阻大几个数量级的电阻率随磁场的变化，2007年诺贝尔奖授予了巨磁阻的发现。获得量子材料的应用性质仍然是难以捉摸的，缺乏对其物理性质的理解是实现这一目标的主要障碍。获得量子材料的应用性质仍然是难以捉摸的。我们对这些材料的性质的绝大多数知识来自于大量的探针，这些探针提供了关于这些材料中奇异相的详细信息。然而，对于与外部世界的接口，重要的是要了解表面和界面对其涌现属性的影响。这些影响将为控制其属性提供新的机会，这可能导致全新的功能。对于突现磁序，我们目前对这些材料中表面的影响的了解几乎为零，因此本提案旨在建立独特的新能力。这里提出的研究计划将解决这一问题，并导致（1）理解表面和界面对突现磁序的影响，（2）开发新的方法用于原子尺度成像和表征磁结构和磁激发（3）探索新的方法来控制新兴的磁状态在减少的维度这将通过一个多方面的方法相结合的方法，探测磁状态在不同的深度从表面实现，从而使一个完整的表征表面或界面上的新兴磁状态的影响。

The properties of normal metals and insulators are quite well understood and numerical calculations of the electronic structures provide often astonishing precision, enabling a computational approach to designing materials with a specific property. This level of understanding has been instrumental in the development of semiconductor electronics. Quantum Materials exhibit a vast range of desirable properties, enabling new functionality, however these are usually unexpected and their properties cannot be predicted. Prime examples for the surprising properties of quantum materials are colossal magnetoresistance and high-temperature superconductivity. High temperature superconductivity occurs at temperatures of almost ten times higher than in conventional superconductors (except under pressure), whereas colossal magnetoresistance exhibits a change in resistivity with magnetic field which is orders of magnitude larger than for giant magnetoresistance, for the discovery of which the Nobel prize was awarded in 2007. Reaping the properties of quantum materials for applications has remained elusive, and a lack of understanding of their physics is a major obstacle to achieving this.Reaping the properties of quantum materials for applications has remained elusive. The vast majority of our knowledge about the properties of these materials comes from bulk probes which have provided information about the exotic phases in these materials with exquisite detail. Yet for interfacing to the outside world, it is important to understand the impact of surfaces and interfaces on their emergent properties. The impact of these will provide new opportunities to control their properties, which might lead to entirely new functionalities. For emergent magnetic orders, our knowledge about the impact of the surface in these materials is currently practically zero, therefore this proposal aim to build unique new capability.The here proposed research programme will address this, and lead to(1) An understanding of the impact of surfaces and interfaces on emergent orders, which are critical to technological exploitation(2) Development new methods for atomic scale imaging and characterization of magnetic structure and magnetic excitations(3) Exploration of novel ways to control emergent magnetic states in reduced dimensionalitiesThis will be achieved through a multi-faceted approach combining methods which probe magnetic states at different depths from the surface, thereby enabling a complete characterization of the surface or interface impact on emergent magnetic states.