Superconductivity and magnetism at and above 38K in molecular materials

金属用于电力传输，但由于电阻，能量以热的形式损失。超导体没有电阻，可以携带电能而不损失能量，因此找到在尽可能高的温度下工作的超导体是重要的。大多数超导体都有由原子组成的简单结构，但最近发现了由规则固体结构中的分子组成的超导体。最近，基于富勒烷的分子超导体体系的研究小组发现了分子超导体的最高工作温度(38K)。我们发现，与超导电性竞争的电子基态是磁性有序的--对于激活电子在S/p轨道上的材料，这种有序也发生在很高的温度(46K)。我们展示了如何用化学计量比Cs3C60控制C60分子在固体中的准确排列，使其从绝缘磁序状态切换到零电阻超导状态。在这个项目中，我们将利用这些发现带来的新机会。我们将确定决定在新的富勒里德系统中采用超导或磁基态的因素。我们将开发新的分子结构家族，S/p电子基超导体和磁体具有增强的性能，以一种可以理解的方式控制晶体对称性、轨道简并和晶格堆积。为了实现这一目标，我们将使用我们首创的基于聚焦溶液的合成方案，结合常压和高压下的结构和物理性质测量以及高级电子结构计算。该项目将探索固体中相关电子行为的独特方面，即电子的行为由它们之间的库仑斥力决定。这是凝聚态科学中最重要的当代问题之一。富勒烯基固体的高分子和晶格对称性为我们提供了一个机会，可以在与以前研究的材料性质不同的条件下研究强关联电子，从而将我们对分子超导和磁性以及金属-绝缘体转变的理解带入一个前所未有的高级阶段。该计划利用了两位主要研究人员的互补专业知识，并将导致具有不可预测和理论挑战性质的新一代基于富勒烯的分子材料。

Metals are used for electricity transmission, but energy is lost as heat because of electrical resistance. Superconductors have no electrical resistance and can carry electricity without losing energy, so finding superconductors which work at as high a temperature as possible is important. Most superconductors have simple structures built from atoms, but recently superconductors made from molecules arranged in regular solid structures have been found. Recent work by the proposing groups on molecular fulleride-based systems led to the discovery of the highest working temperature (at 38 K) for a molecular superconductor. We found that the electronic ground state which is in competition with superconductivity is magnetically ordered - this ordering also occurs at a very high temperature (46K) for a material where the active electrons are in orbitals of s/p parentage. We showed how the exact arrangement of the C60 molecules in the solid with stoichiometry Cs3C60 can be controlled to switch on the zero-resistance superconducting state from the insulating magnetically ordered state. In this project we will exploit the newly presented opportunities arising from these discoveries. We will identify the factors responsible for determining whether superconducting or magnetic ground states are adopted in new fulleride systems. We will develop new structural families of molecular, s/p electron-based superconductors and magnets with enhanced properties, controlled in an understandable manner by crystal symmetry, orbital degeneracy and lattice packing. In order to achieve this, we will use focussed solution-based synthetic protocols that we have pioneered, combined with structural and physical property measurements at ambient and high pressure and high-level electronic structure calculations. The project will explore unique aspects of the behavior of correlated electrons in solids i.e. electrons whose behavior is determined by their mutual Coulomb repulsion. This is one of the most important contemporary problems in condensed matter science. The high molecular and lattice symmetry of fullerene-based solids offers an opportunity to study strongly correlated electrons under conditions that are qualitatively different from previously studied materials, and therefore to take our understanding of molecular superconductivity and magnetism and the metal-insulator transition to an unprecedentedly advanced stage. The programme exploits the complementary expertise of the two principal investigators and will lead to a new generation of novel fullerene-based molecular materials with unpredictable and theoretically challenging properties.