Tuning order from disordered ground states in geometrically frustrated classical "non-hbar" materials

凝聚态物理已经发展出一套相对完整的材料常见相理论，导致了许多具有重要技术意义的设备，包括电子屏幕、存储器和开关设备。朗道，或平均场理论，提供了一个框架来模拟、预测和理解各种令人惊讶的不同材料和动力系统中的相和相变。虽然这些传统的基态已被证明在技术上具有重要意义，其基本理论代表着科学家的重大成功，但事实证明，这些阶段非常难以抑制，而且往往在寻求或设计新材料特性时出现。要发现将导致新材料革命的新相，需要抑制这些共同的阶段，以便出现奇异和非传统的性质。最常见的关闭材料中常规相的工具是通过化学掺杂引入无序，从而产生强烈的随机场。许多重要的理论被用来描述随机场的效应，特别是用来解释表面自由能和体积自由能之间的微妙平衡。然而，无序的使用已被证明是有限的，因为性质经常被模板化到材料中，并且不能直接控制，并且所产生的材料的基态也很难理解。另一种最近在过去十年中探索的抑制传统相位的方法是引入强烈的波动。虽然这可以通过温度微不足道地完成，但通过研究量子系统已经出现了新的相，在量子系统中，物理受到量子力学和海森堡测不准原理的支配。对量子系统的研究导致了许多新的物质相的发现，包括高温超导体和量子自旋液体，其中的磁性在任何温度下都是动态的。量子涨落的一个限制是，这些性质不会直接传递到基于铁电的系统，也不会直接传递到磁性和结构性质强烈耦合的多铁性。此外，由于基态的强烈波动性质，还没有发现这些性质是容易调节的，从而限制了立即用于应用。因此，这一提议旨在通过研究经典受挫系统来走一条不同的路线，在这些系统中，大的基态简并通过晶格自然地引入，而量子力学效应很小。重点将放在基于三角形几何的晶格上。量子系统中没有强烈的涨落，这就提供了在不同基态之间可控调谐的能力，使这条路线成为创造新开关设备或新型存储系统的潜在手段。该提案旨在研究经典受挫的磁体和铁电材料。这些系统可以在一个共同的框架内描述，并将使用散射技术进行研究，以提供基态的大量真实空间图像。这些特性将通过磁场和电场进行调节，为发现技术上适用的材料提供了一条直接的途径。研究铁电体和磁体的综合方法将导致对适用于直接工业应用的完整理解。这些新材料将导致新相的发现，包括新的高温多铁性，经典的自旋液体，或局域可控边界或缺陷。

Condensed matter physics has developed a relatively complete theory of common phases in materials leading to many technologically important devices including electronic screens, memory storage, and switching devices. Landau, or mean-field theory, has provided a framework to model, predict, and understand phases and transitions in a surprisingly diverse variety of materials and also dynamical systems. While these conventional ground states have proven technologically important and the underlying theory represents a major success for scientists, these phases have proven incredibly difficult to suppress and often emerge when new materials properties are sought or engineered.To discover novel phases that will lead to a new materials revolution, these common phases need to be suppressed to allow exotic and unconventional properties to emerge. The most common vehicle to turn off conventional phases in materials has been through the introduction of disorder through chemical doping resulting in strong random fields. Many important theories have been formulated and tested to describe the effects of random fields and in particular to account for the fine balance between surface and bulk free energy. However, the use of disorder has proved limiting as properties are often templated into the material and not directly controllable and also the resulting ground state of the material is difficult to understand. Another route, which has more recently been explored in the last decade, to suppress conventional phases is by introducing strong fluctuations. While this can be trivially done with temperature, new phases have emerged by studying quantum systems where the physics are governed by quantum mechanics and the Heisenberg uncertainty principle. The study of quantum systems has resulted in the discovery of many new phases of matter including high temperature superconductors and also quantum spin-liquids where the magnetism is dynamic at any temperature. A limitation of quantum fluctuations is that the properties do not carry over directly to ferroelectric based systems and also multiferroics where magnetic and structural properties are strongly coupled. Also, owing to the strong fluctuating nature of the ground state, the properties have not been found to be easily tunable limiting immediate use for applications. This proposal aims to therefore take a different route by studying classically frustrated systems where a large ground state degeneracy is introduced naturally through the lattice and quantum mechanical effects are small. Emphasis will be placed on lattices based upon a triangular geometry. The lack of strong fluctuations (that exists in quantum systems) provides the ability to controllably tune between different ground states making this route a potential means of creating new switching devices or novel memory storage systems.The proposal aims to investigate classically frustrated magnets and ferroelectrics. These systems can be described within a common framework and will be studied using scattering techniques to provide a bulk real space image of the ground state. The properties will be tuned with magnetic and electric fields supplying a direct route for discovering a new route towards technologically applicable materials. The combined approach of investigating ferroelectrics and magnets will result in a complete understanding applicable to immediate industrial applications. These new materials will lead to the discovery of new phases including new high temperature multiferroics, classical spin liquids, or localized controllable boundaries or defects.