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

凝聚态物理学已经发展了一个相对完整的理论，在材料中的共同阶段，导致许多技术上重要的设备，包括电子屏幕，存储器和开关设备。朗道，或平均场理论，提供了一个框架来建模，预测和理解各种各样的材料和动力学系统中的相变。虽然这些常规基态已被证明在技术上具有重要意义，其基础理论也代表了科学家们的重大成功，但这些相已被证明非常难以抑制，并且经常在寻求或设计新材料特性时出现。为了发现将导致新材料革命的新相，这些常见相需要被抑制，以允许奇异和非常规特性出现。关闭材料中常规相的最常见手段是通过化学掺杂引入无序，从而产生强随机场。许多重要的理论已经制定和测试，以描述随机场的影响，特别是占表面和体积自由能之间的精细平衡。然而，无序的使用已被证明是有限的，因为性质通常被模板化到材料中并且不直接可控，并且材料的所得基态也难以理解。另一种抑制常规相的方法是引入强涨落，这是在过去十年中进行的探索。虽然这可以通过温度来完成，但通过研究量子系统已经出现了新的阶段，其中物理学由量子力学和海森堡不确定性原理控制。对量子系统的研究已经发现了许多新的物质相，包括高温超导体和量子自旋液体，其中磁性在任何温度下都是动态的。量子涨落的局限性在于其性质不会直接传递到基于铁电的系统以及磁性和结构性质强烈耦合的多铁性。此外，由于基态的强波动性质，尚未发现这些性质是容易调节的，限制了直接用于应用。因此，这项建议的目的是采取不同的路线，通过研究经典的挫折系统，其中一个大的基态简并自然引入通过晶格和量子力学效应是小的。重点将放在基于三角形几何的晶格上。缺乏强涨落（存在于量子系统中）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器件或新型存储器存储系统的潜在手段。该提议旨在研究经典受抑磁体和铁电体。这些系统可以在一个共同的框架内进行描述，并将使用散射技术进行研究，以提供一个散装的真实的空间图像的基态。这些特性将通过磁场和电场进行调整，为发现技术适用材料的新途径提供直接途径。研究铁电体和磁体的组合方法将导致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，或局部可控的边界或缺陷。

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.