Investigation of the strange metal normal state of electron-doped oxide superconductors

电子掺杂氧化物超导体奇异金属正常态的研究

• 批准号: 2002658
• 负责人: richard greene
• 金额: $ 48万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2002658&HistoricalAwards=false
• 关键词: Investigation; strange; metal; normal; state

Non-technical abstractSuperconductivity, the complete absence of electrical resistance, is an amazing low temperature property of some elements and compounds. This property of solids was discovered in 1911 and was believed to be fully understood in 1957 by the Bardeen, Cooper, Schrieffer (BCS) theory. In 1987 some copper oxide compounds (cuprates) were discovered with unexpectedly high superconducting transition temperatures (up to 140 Kelvin). This high-temperature superconductivity cannot be explained by the conventional BCS mechanism and it is not presently understood. A complete understanding of high-temperature superconductivity is one of the major unsolved problems of condensed matter physics. The solution to this problem could lead to the discovery of room temperature (300 Kelvin) superconductors, a development with very significant practical applications. This project performs experimental studies on one class of cuprate compounds where the superconductivity can be completely eliminated by the application of a small magnetic field. This enables the non-superconducting, or normal, metallic state to be studied over a wide range of temperature from 600 K to well below 1K. The normal state of the cuprates has quite different physical properties from those of well-known metals, such as copper or lead, and the cuprates have been called strange metals. An understanding of this strange metal state is believed to be crucial for an understanding of the origin of the superconductivity. In this project a variety of transport and other experiments are performed on specially prepared thin films. Variation of the magnetic field, the temperature and electron doping can change the normal state properties in ways that are expected to give deep insight into the nature of the strange metal state and the superconductivity. This project supports the education of PhD and undergraduate students at the University of Maryland---an urban university with a diverse population---in advanced vacuum deposition and electrical characterization techniques. These techniques have proven to be excellent training for productive scientific careers in academic and technology settings.Technical abstractUnderstanding the mechanism of superconductivity and the non-Fermi liquid (strange metal) normal state in strongly correlated oxides is one of the most significant unsolved problems of condensed matter physics. Recently some dramatic experimental results have been reported by the PI (and others) that give new insights into the physics of the copper oxides (cuprates) and that also report the discovery of superconductivity in a related nickelate system, Sr doped NdNiO2. This project follows up on these breakthroughs to gain a more detailed understanding of the strange normal state of the electron-doped cuprates and the doped nickelates. This project provides a comprehensive set of experiments to study the nature of the normal state when superconductivity is suppressed, either by magnetic field, disorder or critical current. The electron-doped cuprates are particularly advantageous for this research because the low temperature normal state (0 T Tc) can be reached with a modest dc magnetic field (H 10 T). An understanding of the nature of the normal state of the cuprates is believed to be crucial for understanding the cause of high-temperature superconductivity in the cuprates. The experimental techniques used are resistivity, Hall Effect, magnetoresistance, Nernst effect, thermopower, specific heat and strain (pressure). Some transport experiments are done at very high magnetic field at the NSF supported National High Magnetic Field Laboratory (NHMFL) in Tallahassee and Los Alamos. The research includes an in-depth study of the itinerant ferromagnetism discovered by the PI in 2019 in the highly doped region of the n-type cuprates The combination of materials science expertise and physics measurement expertise of the PI is essential for making progress in this very important area of correlated physics materials research. This project incorporates the training of high-school students, undergraduate science majors, graduate students, and postdoctoral scientists in various experimental aspects of condensed matter physics research. As in the past, the principal investigator will encourage women and underrepresented groups to participate in this project. The external collaborations in this project provide a unique vehicle for students to experience research in different laboratory environments, i.e., university, industry, and government. An ongoing participation in the Graduate Resources Advancing Diversity (GRADMAP) program at the University of Maryland will involve undergraduates in research exposure programs designed to attract a broader audience to graduate studies. Efforts to encourage a broader education in science via existing Physics department outreach programs with predominately minority public-school students near the University of Maryland will be continued. These include, Physics is Phun, Physics Discovery Days, and the Summer School Girl’s Program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术摘要超导性，完全没有电阻，是某些元素和化合物的一种惊人的低温特性。 固体的这种性质在1911年被发现，并被认为在1957年被BCS理论完全理解。1987年，一些氧化铜化合物（铜酸盐）被发现具有出乎意料的高超导转变温度（高达140开尔文）。 这种高温超导性不能用传统的BCS机制来解释，目前还不清楚。对高温超导性的完整理解是凝聚态物理学尚未解决的主要问题之一。 这个问题的解决可能会导致室温（300开尔文）超导体的发现，这是一个具有非常重要的实际应用的发展。本项目对一类铜酸盐化合物进行实验研究，通过施加小磁场可以完全消除超导性。这使得非超导或正常的金属状态能够在从600 K到远低于1 K的广泛温度范围内进行研究。铜酸盐的正常状态具有与铜或铅等已知金属完全不同的物理性质，因此铜酸盐被称为奇异金属。理解这种奇怪的金属状态被认为是理解超导起源的关键。在这个项目中，各种运输和其他实验进行专门准备的薄膜。 磁场、温度和电子掺杂的变化可以改变正常态的性质，从而有望深入了解奇怪金属态和超导性的本质。 该项目支持马里兰州大学-一所人口多样化的城市大学-的博士生和本科生在先进的真空沉积和电特性技术方面的教育。这些技术已被证明是优秀的培训生产性的科学事业在学术和技术settings.Technical abstractUnderstanding超导性和非费米液体（奇怪的金属）正常状态的机制在强关联氧化物是凝聚态物理学的最重要的未解决的问题之一。最近，PI（和其他人）报道了一些引人注目的实验结果，这些结果对铜氧化物（铜酸盐）的物理学提供了新的见解，并且还报道了在相关的镍酸盐系统中发现超导性，Sr掺杂的NdNiO 2。该项目跟进这些突破，以更详细地了解电子掺杂铜酸盐和掺杂镍酸盐的奇怪正常状态。该项目提供了一套全面的实验来研究超导性被抑制时正常状态的性质，无论是通过磁场，无序还是临界电流。电子掺杂的铜酸盐是特别有利的这项研究，因为低温正常状态（0 T Tc）可以达到一个温和的直流磁场（H 10 T）。理解铜氧化物正常态的性质被认为是理解铜氧化物高温超导性的原因的关键。所用的实验技术有电阻率、霍尔效应、磁阻、能斯特效应、热功率、比热和应变（压力）。在塔拉哈西和洛斯阿拉莫斯的美国国家科学基金会支持的国家高磁场实验室（NHMFL）进行了一些运输实验。该研究包括深入研究PI于2019年在n型铜氧化物的高掺杂区域发现的巡回铁磁性PI的材料科学专业知识和物理测量专业知识的结合对于在相关物理材料研究的这一非常重要的领域取得进展至关重要。该项目包括高中生，本科科学专业，研究生和博士后科学家在凝聚态物理研究的各个实验方面的培训。同过去一样，主要调查员将鼓励妇女和代表性不足的群体参与这一项目。该项目的外部合作为学生提供了一个独特的工具，让他们在不同的实验室环境中体验研究，即，大学、工业和政府。正在进行的参与研究生资源推进多样性（GRADMAP）计划在马里兰州的大学将涉及本科生的研究曝光计划，旨在吸引更广泛的观众研究生学习。 通过现有的物理系外展计划，鼓励在马里兰州大学附近的主要少数民族公立学校的学生更广泛的科学教育的努力将继续下去。这些奖项包括物理是Phun、物理发现日和暑期学校女生项目。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Counterexample to the conjectured Planckian bound on transport

推测的普朗克运输约束的反例

• DOI: 10.1103/physrevb.104.235138
• 发表时间: 2021
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Poniatowski, Nicholas R.;Sarkar, Tarapada;Lobo, Ricardo P.;Das Sarma, Sankar;Greene, Richard L.
• 通讯作者: Greene, Richard L.

BCS d -wave behavior in the terahertz electrodynamic response of electron-doped cuprate superconductors

电子掺杂铜酸盐超导体太赫兹电动响应中的 BCS d 波行为

• DOI: 10.1103/physrevb.104.064501
• 发表时间: 2021
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Tagay, Zhenisbek;Mahmood, Fahad;Legros, Anaelle;Sarkar, Tarapada;Greene, Richard L.;Armitage, N. P.
• 通讯作者: Armitage, N. P.

Hidden strange metallic state in underdoped electron-doped cuprates

欠掺杂电子掺杂铜酸盐中隐藏的奇怪金属态

• DOI: 10.1103/physrevb.103.224501
• 发表时间: 2021
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Sarkar, Tarapada;Poniatowski, Nicholas R.;Higgins, Joshua S.;Mandal, P. R.;Chan, Mun K.;Greene, Richard L.
• 通讯作者: Greene, Richard L.

Anomalous normal-state magnetotransport in an electron-doped cuprate

电子掺杂铜氧化物中的反常常态磁输运

• DOI: 10.1103/physrevb.103.125102
• 发表时间: 2021
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Poniatowski, Nicholas R.;Sarkar, Tarapada;Greene, Richard L.
• 通讯作者: Greene, Richard L.

Resistivity saturation in an electron-doped cuprate

电子掺杂铜酸盐中的电阻率饱和

• DOI: 10.1103/physrevb.103.l020501
• 发表时间: 2021
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Poniatowski, Nicholas R.;Sarkar, Tarapada;Das Sarma, Sankar;Greene, Richard L.
• 通讯作者: Greene, Richard L.