A study of unconventional transport in electron-doped oxide superconductors

电子掺杂氧化物超导体的非常规输运研究

• 批准号: 1708334
• 负责人: richard greene
• 金额: $ 45万
• 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: 2017
• 资助国家: 美国
• 起止时间: 2017-08-01 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1708334&HistoricalAwards=false
• 关键词: study; unconventional; transport; electron; doped

Non-Technical Abstract:Superconductivity, the complete absence of electrical resistance, is an amazing low temperature property of some elements and compounds. This quantum 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 focuses on experimental transport studies on one class of cuprate compounds where the superconductivity can be completely suppressed by the application of a small magnetic field. This enables the normal metallic state to be studied over a full range of temperature from 300 K to well below 1K. An understanding of the normal metal state is believed to be crucial for a full understanding of the origin of the superconductivity. The transport experiments are planned on specially prepared thin films with variation of the magnetic field, the temperature and electron doping, all of which change the normal state properties in ways that are expected to give deep insight into the nature of 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 electronic characterization techniques. These techniques have proven to be excellent training for productive scientific careers in academic and technology settings.Technical Abstract:Understanding the mechanism of superconductivity and the non-Fermi liquid normal state in strongly correlated copper oxides (cuprates) is one of the most significant unsolved problems of condensed matter physics. Much progress has been made, but there are still many puzzles to be solved. In the last few years some dramatic new experimental results have been found that give new insights into the physics of the hole-doped cuprates. Since hole- and electron-doped cuprates should obey the same fundamental physics, the goal of this project is to gain a more detailed understanding of the normal state and superconducting properties of the electron-doped (n-doped) cuprate superconductors. This new information should allow the mechanism of the unconventional superconductivity in all cuprates to be determined. A comprehensive set of experiments helps understand the nature of the normal state when superconductivity is suppressed by a magnetic field. The n-doped cuprates are particularly advantageous for this 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-Tc superconductivity in both n- and p-type cuprates. The experimental techniques to be used are: resistivity, Hall Effect, magnetoresistance, Nernst effect, thermopower, and tunneling. Some transport experiments are performed at very high magnetic field at the NSF supported high magnetic field labs in Tallahassee and Los Alamos. A study of the superconducting state in the over doped region of the electron-doped phase diagram is also to be done, since anomalous behavior recently found there is suggestive of fundamentally new physics. With outside collaborators, penetration depth, high-field Nernst and thermal diffusivity experiments are attempted. 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 encourages 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 involves 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 are continued. These include, Physics is Phun, Physics Discovery Days, and the Summer School Girl's Program.

非技术摘要：超导性，完全没有电阻，是某些元素和化合物的惊人低温特性。 1911年发现了这种固体的量子特性，并被认为是由Bardeen，Cooper，Schrieffer（BCS）理论完全理解的。 1987年，发现了一些氧化铜化合物（铜），并具有出乎意料的高超导过渡温度（高达140 kelvin）。 传统的BCS机制无法解释这种高温超导性，目前尚未理解。对高温超导性的完全理解是凝结物理学的主要未解决问题之一。 解决此问题的解决方案可能导致发现室温（300 Kelvin）超导体，这是具有非常重要的实际应用的开发。该项目的重点是对一类库酸酯化合物的实验运输研究，在该化合物中，可以通过应用小磁场完全抑制超导性。这使得正常的金属状态可以在从300 K到1K以下的整个温度范围内进行研究。人们认为，对正常金属状态的理解对于对超导性的起源充分理解至关重要。计划在具有磁场变化，温度和电子掺杂的特殊制备的薄膜上进行运输实验，所有这些薄膜都以期望对超导性的性质进行深入了解的方式改变了正常状态的特性。 该项目支持马里兰大学的博士学位和本科生的教育 - 一所城市大学，人口多样化 - 高级真空沉积和电子表征技术。事实证明，这些技术是在学术和技术环境中为生产性科学职业提供的出色培训。技术摘要：了解超导性的机制和在密切相关的铜氧化物（Cuprates）中的非Fermi液体正常状态是凝结物理学的最重要的未解决问题之一。已经取得了很多进展，但是仍然有很多难题可以解决。 在过去的几年中，发现一些戏剧性的新实验结果，可以对掺杂孔的丘比特的物理学有新的见解。由于孔和电子掺杂的铜层应遵守相同的基本物理，因此该项目的目的是对正常状态和电子掺杂（N掺杂）丘比特超导体的正常状态和超导性特性有更详细的了解。 这些新信息应允许确定所有丘陵中非常规超导性的机制。 当磁场抑制超导性时，一组全面的实验有助于理解正常状态的性质。 N掺杂的酸粉菜对此特别有利，因为可以使用适度的DC磁场（H 10 T）达到低温正常状态（0 T TC）。据信，对铜酸盐正常状态的性质的理解对于理解n-和p型蛋白酶的高-TC超导性的原因至关重要。要使用的实验技术是：电阻率，霍尔效应，磁性，Nernst效果，热电器和隧道。一些运输实验是在NSF支持的高磁场实验室和塔拉哈西和洛斯阿拉莫斯的高磁场实验室的非常高的磁场上进行的。还将对电子掺杂相位图的过度掺杂区域中的超导状态进行研究，因为最近发现有根本上有新的物理学的异常行为。借助外部协作者，尝试了穿透深度，高场Nernst和热扩散实验。该项目纳入了高中生，本科科学专业，研究生和博士后科学家的培训，这些培训是在凝聚态物理学研究的各个实验方面的培训。与过去一样，主要研究人员鼓励妇女和代表性不足的团体参加该项目。该项目的外部合作为学生提供了独特的工具，可以在不同的实验室环境（即大学，工业和政府）中进行研究。马里兰州大学持续参与多样性的研究生资源（GradMAP）计划涉及研究曝光计划的本科生，旨在吸引更广泛的受众学习研究生学习。 通过现有的物理学系外展计划鼓励在科学领域进行更广泛的教育，继续马里兰大学附近的主要少数公立学校学生。其中包括物理学是Phun，Physics Discovery Days和The Summer School Girl的计划。

项目成果

The Strange Metal State of the Electron-Doped Cuprates

• DOI: 10.1146/annurev-conmatphys-031119-050558
• 发表时间: 2020-01-01
• 期刊: ANNUAL REVIEW OF CONDENSED MATTER PHYSICS, VOL 11, 2020
• 作者: Greene, Richard L.;Mandal, Pampa R.;Sarkar, Tarapada
• 通讯作者: Sarkar, Tarapada

Ferromagnetic order beyond the superconducting dome in a cuprate superconductor

• DOI: 10.1126/science.aax1581
• 发表时间: 2020-05-01
• 期刊: SCIENCE
• 影响因子: 56.9
• 作者: Sarkar, Tarapada;Wei, D. S.;Greene, Richard L.
• 通讯作者: Greene, Richard L.

Correlation between scale-invariant normal-state resistivity and superconductivity in an electron-doped cuprate

• DOI: 10.1126/sciadv.aav6753
• 发表时间: 2019-05-01
• 期刊: SCIENCE ADVANCES
• 影响因子: 13.6
• 作者: Sarkar, Tarapada;Mandal, P. R.;Greene, Richard L.
• 通讯作者: Greene, Richard L.

Quantum oscillations from the reconstructed Fermi surface in electron-doped cuprate superconductors

电子掺杂铜酸盐超导体中重建费米表面的量子振荡

• DOI: 10.1088/1367-2630/aab7e7
• 发表时间: 2018
• 期刊: New Journal of Physics
• 影响因子: 3.3
• 作者: Higgins, J S;Chan, M K;Sarkar, Tarapada;McDonald, R D;Greene, R L;Butch, N P
• 通讯作者: Butch, N P

Three-dimensional collective charge excitations in electron-doped copper oxide superconductors

• DOI: 10.1038/s41586-018-0648-3
• 发表时间: 2018-11-15
• 期刊: NATURE
• 影响因子: 64.8
• 作者: Hepting, M.;Chaix, L.;Lee, W. S.
• 通讯作者: Lee, W. S.