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Resonant detection of electronic nematicity in correlated electron systems

相关电子系统中电子向列性的共振检测

基本信息

批准号：
299282802
负责人：
Professor Dr. Philip Moll
金额：
--
依托单位：
Abteilung für Mikrostrukturierte Quantenmaterie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/299282802?language=en
关键词：
Resonant detection electronic nematicity correlated

项目摘要

In normal metals, the electronic states are governed merely by their interaction with the atomic lattice, and as a result the electronic system inherits its symmetries from the hosting lattice. However, if the interactions between the electrons themselves are sufficiently strong, this simple paradigm must not hold true anymore and intriguing strongly correlated states of lower symmetry than the parent crystal may arise: An electronic nematic state breaks a rotational symmetry while the translational symmetry of the crystal remains intact, named in analogy to the nematic phase in liquid crystals. A hallmark of such states is a pronounced scattering time anisotropy between symmetry related directions. Small external lattice distortions influence the preferred direction of the nematic electronic system, yielding a substantial dependence of the resistance on uniaxial strain. Electronic nematicity has been argued to be of importance for the strong electron correlations in both copper- and iron-based high-temperature superconductors. Nematicity is a rather rare phenomenon, observed only in a handful of systems, and its potential appearance in both known high-Tc classes naturally leads to a fundamental question: Do nematic fluctuations contribute to Cooper pairing, or is nematicity a competing phenomenon irrelevant or even disadvantageous for high-Tc superconductivity? We intend to quantitatively measure the nematic susceptibility in a wide range of pnictide superconductors and correlate it with the transition temperature Tc. Many classes of iron-arsenides are inaccessible to traditional measurement techniques due to the small size of available single crystals. We propose to develop a highly-sensitive resonant nematicity detection method based on Focused Ion Beam (FIB) carved single crystal microresonators. By carving 100-10 micrometer long mechanical oscillators out of pnictide single crystals, we exploit the compression and expansion of the material during a bending mode cycle to directly measure the nematic susceptibility with higher precision and accuracy compared to existing methods. At the same time, the resonance frequency of the cantilever devices will provide a direct measure of the elastic constants of the system. This would enable us to correlate the nematic susceptibility with a thermodynamic property of the ionic lattice, which is a key comparison to identify the degree of the nematic contribution to the symmetry breaking. This project is aimed to provide a comprehensive comparison of nematicity in the various structural classes of pnictide superconductors, and investigate its role in superconductivity. Once this new technique has been developed, it will be a versatile tool to research nematic phenomena in a variety of other materials beyond iron-based superconductors.

在正常金属中，电子态仅仅由它们与原子晶格的相互作用决定，因此电子系统从宿主晶格继承了它的对称性。然而，如果电子之间的相互作用足够强，这个简单的范例就不再成立，可能会出现比母晶体更低对称性的有趣的强关联态：电子的双态打破了旋转对称性，而晶体的平移对称性保持不变，类似于液晶中的双相。这种状态的一个标志是对称相关方向之间的明显的散射时间各向异性。小的外部晶格畸变的影响的首选方向的电子系统，产生的单轴应变的电阻的实质性依赖。电子向列性对于铜基和铁基高温超导体中的强电子关联具有重要意义。向列性是一种相当罕见的现象，只在少数系统中观察到，其潜在的外观在两个已知的高Tc类自然会导致一个基本的问题：做？涨落有助于库珀配对，或者是向列性的竞争现象无关，甚至不利于高Tc超导性？我们打算定量地测量在广泛的磷属元素化物超导体的磁化率，并将其与转变温度Tc。许多种类的铁砷化物由于可用单晶的小尺寸而无法用传统的测量技术测量。提出了一种基于聚焦离子束（FIB）刻蚀单晶微谐振器的高灵敏度共振向列性检测方法。通过从磷族元素化物单晶中雕刻出100-10微米长的机械振荡器，我们利用弯曲模式循环期间材料的压缩和膨胀来直接测量磁化率，与现有方法相比具有更高的精度和准确度。同时，悬臂装置的共振频率将提供系统的弹性常数的直接测量。这将使我们能够将磁化率与离子晶格的热力学性质相关联，这是确定磁化率对对称性破缺的贡献程度的关键比较。本计画的目的是提供各种结构类别的磷属元素化物超导体中向列性的全面比较，并探讨其在超导电性中的作用。一旦这项新技术被开发出来，它将成为研究铁基超导体以外各种其他材料中超导现象的多功能工具。