The control of electrons through patterning of superstructures

通过上部结构图案化控制电子

• 批准号: EP/J011150/1
• 负责人: J P Goff
• 金额: $ 62.77万
• 依托单位: Royal Holloway University of London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FJ011150%2F1
• 关键词: control; electrons; through; patterning; superstructures

As concern grows over the environment, energy generation and climate change, there will be an increasing demand for new materials with improved performance to make technological applications cleaner and more efficient. One way to go about optimizing a material's performance is to start with a simple 'parent' compound and vary its chemical composition in a continuous and systematic way, for example, by substituting one of its chemical constituents by another. This strategy, known as doping, has been extremely successful. For example, in 1988, J.G. Bednorz and K.A. Müller replaced about 15% of the La ions in the insulating ceramic La2CuO4 with Ba and found that the product became a superconductor (i.e. lost all its electrical resistance) at an unprecedented temperature of 35 K, significantly higher than the previous highest known superconducting temperature. This discovery was the starting point for the development of the high temperature copper oxide superconductors, which now have operating temperatures as high as 135 K and which are increasingly being used in applications where high magnetic fields or electric currents are required. Although the consequences of doping can be spectacular (witness the copper oxide superconductors) they can also be complex, and the link to changes in physical properties is not always well understood. One effect that can play an important role is the formation of superstructures, in which either the dopant atoms or the charges they transfer to the host organise themselves into patterns which extend over long distances and are periodically modulated on a nanometre scale. Superstructures modify the electrostatic potential in the host material, which can in turn strongly influence the physical properties of the material. This raises an interesting possibility: If one can control the formation of superstructures then it should be possible to tune the properties of a material and thereby enhance its performance.The aims of this project are twofold, first, to understand why superstructures occur in certain materials and, secondly, to study the consequences of superstructure formation for the physical properties of those materials. To provide a testing ground for these ideas we have identified several different materials in which superstructures appear to play a prominent role. These include sodium cobaltate (a very promising p-type thermoelectric material), lithium cobaltate (the main component of the type of rechargeable batteries used in mobile phones and laptops), and two recently-discovered iron-based high temperature superconductors. As well as being good models on which to conduct experiments, these systems are chosen because they offer good prospects to underpin technological solutions for environmental and societal issues through their potential to improve the efficiency of energy harvesting and storage devices.We will prepare single crystal samples whose composition can be varied via different doping strategies. X-ray and neutron scattering will be employed to probe deep inside the crystals to reveal the presence of superstructures and to refine the associated structural and electronic patterns, and we will correlate the results with bulk measurements of the electrical, thermal and magnetic properties of the materials. With the help of theoretical modelling, our programme will lead to a clearer understanding of the degree to which superstructures can be used control physical behaviour, and will contribute towards the development of materials with improved performance for practical applications.

随着人们对环境、能源生产和气候变化的日益关注，对具有更高性能的新材料的需求将日益增加，以使技术应用更清洁、更高效。优化材料性能的一种方法是从一种简单的“母体”化合物开始，以连续和系统的方式改变其化学成分，例如，用另一种化学成分取代其中一种化学成分。这种被称为兴奋剂的策略非常成功。例如，在1988年，J.G. Bednorz和K.A.穆勒用Ba取代了绝缘陶瓷La2CuO4中约15%的La离子，并发现该产品在前所未有的35 K温度下成为超导体（即失去所有电阻），明显高于之前已知的最高超导温度。这一发现是高温氧化铜超导体发展的起点，其现在的工作温度高达135 K，并且越来越多地用于需要高磁场或电流的应用中。虽然掺杂的后果可能是壮观的（见证氧化铜超导体），但它们也可能是复杂的，并且与物理性质变化的联系并不总是很好地理解。一个可以发挥重要作用的效应是形成超结构，其中掺杂剂原子或它们转移到主体的电荷将自己组织成长距离延伸的图案，并在纳米尺度上进行周期性调制。超结构改变了主体材料中的静电势，这反过来可以强烈影响材料的物理性质。这就提出了一个有趣的可能性：如果人们能够控制超结构的形成，那么就有可能调整材料的性能，从而提高其性能。本项目的目的有两个，第一，理解为什么超结构会在某些材料中出现，第二，研究超结构形成对这些材料物理性能的影响。为了给这些想法提供一个试验场，我们已经确定了几种不同的材料，在这些材料中，超结构似乎起着重要的作用。其中包括钴酸钠（一种非常有前途的p型热电材料）、钴酸锂（移动的手机和笔记本电脑中使用的可充电电池类型的主要成分），以及两种最近发现的铁基高温超导体。这些系统不仅是进行实验的良好模型，还因为它们具有提高能量收集和存储设备效率的潜力，为环境和社会问题的技术解决方案提供了良好的前景。我们将制备单晶样品，其组成可以通过不同的掺杂策略来改变。X射线和中子散射将被用来探测晶体内部深处，以揭示超结构的存在，并细化相关的结构和电子模式，我们将把结果与材料的电，热和磁特性的批量测量相关联。在理论建模的帮助下，我们的计划将使人们更清楚地了解超结构可用于控制物理行为的程度，并将有助于开发具有更好性能的材料，用于实际应用。

项目成果

Two-dimensional Cs-vacancy superstructure in iron-based superconductor Cs 0.8 Fe 1.6 Se 2

铁基超导体中的二维Cs空位超结构Cs 0.8 Fe 1.6 Se 2

• DOI: 10.1103/physrevb.91.144114
• 发表时间: 2015
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Porter D

Suppression of thermal conductivity by rattling modes in thermoelectric sodium cobaltate.

• DOI: 10.1038/nmat3739
• 发表时间: 2013-11
• 期刊: Nature materials
• 影响因子: 41.2
• 作者: D. Voneshen;K. Refson;E. Borissenko;M. Krisch;A. Bosak;A. Piovano;E. Cemal;M. Enderle;M. Gutmann;M. Hoesch;M. Roger;L. Gannon;A. Boothroyd;S. Uthayakumar;D. Porter;J. Goff

Hopping Time Scales and the Phonon-Liquid Electron-Crystal Picture in Thermoelectric Copper Selenide.

• DOI: 10.1103/physrevlett.118.145901
• 发表时间: 2017-03
• 期刊: Physical review letters
• 影响因子: 8.6
• 作者: D. Voneshen;H. Walker;K. Refson;K. Refson;J. Goff

Divacancy superstructures in thermoelectric calcium-doped sodium cobaltate

热电钙掺杂钴酸钠的双空位超结构

• DOI: 10.1103/physrevb.90.054101
• 发表时间: 2014
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Porter D

Two-dimensional Cs-vacancy superstructure in iron-based superconductor $Cs_{0.8}Fe_{1.6}Se_2$

铁基超导体中的二维Cs空位超结构$Cs_{0.8}Fe_{1.6}Se_2$

• DOI: 10.48550/arxiv.1505.02527
• 发表时间: 2015
• 作者: Porter D