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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

基本信息

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

项目摘要

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.

摘要：超导性，即完全没有电阻，是某些元素和化合物的一种惊人的低温特性。固体的这种量子特性是在1911年发现的，1957年，人们认为巴丁、库珀、施里弗（BCS）理论完全理解了固体的这种量子特性。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，目前还没有被理解。对高温超导性的完全理解是凝聚态物理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实际应用的发展。本项目主要研究一类铜化合物的实验输运，该类化合物的超导性可以通过施加小磁场来完全抑制。这使得正常的金属状态可以在300 K到远低于1K的整个温度范围内进行研究。对正常金属态的理解被认为是充分理解超导性起源的关键。输运实验计划在特殊制备的薄膜上进行，这些薄膜随磁场、温度和电子掺杂的变化而变化，所有这些都改变了正常状态的性质，有望深入了解超导性的本质。该项目支持马里兰大学（一所人口多样化的城市大学）的博士和本科生在先进真空沉积和电子表征技术方面的教育。这些技术已被证明是在学术和技术环境中从事生产性科学事业的极好训练。技术摘要：了解强相关铜氧化物（cuprates）的超导机制和非费米液体正态是凝聚态物理中最重要的未解决问题之一。取得了很大进展，但仍有许多难题有待解决。近年来，人们发现了一些引人注目的新实验结果，对空穴掺杂铜酸盐的物理学有了新的认识。由于空穴和电子掺杂的铜应该遵循相同的基本物理原理，本项目的目标是更详细地了解电子掺杂（n掺杂）铜超导体的正常状态和超导特性。这一新信息将使所有铜酸盐的非常规超导机制得以确定。一套全面的实验有助于理解超导性被磁场抑制时正常状态的本质。氮掺杂铜酸盐在这方面特别有利，因为在适度的直流磁场（h10 T）下可以达到低温正常状态（0 ttc）。了解铜酸盐正常状态的性质对于理解n型和p型铜酸盐的高tc超导性的原因至关重要。要使用的实验技术有：电阻率、霍尔效应、磁阻、能司特效应、热电和隧道。一些输运实验是在美国国家科学基金会支持的塔拉哈西和洛斯阿拉莫斯的高磁场实验室进行的。对电子掺杂相图中过掺杂区域的超导态的研究也要进行，因为最近在那里发现的异常行为暗示了基本的新物理学。与外界合作者，尝试穿透深度，高场能量和热扩散率实验。本项目包括对高中生、理科生、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。与过去一样，首席研究员鼓励妇女和代表性不足的群体参与这个项目。这个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。马里兰大学正在进行的研究生资源促进多样性（GRADMAP）项目涉及本科生参与旨在吸引更广泛受众的研究生学习的研究项目。通过现有的物理系外展项目，鼓励在马里兰大学附近以少数族裔为主的公立学校学生接受更广泛的科学教育的努力仍在继续。这些活动包括：物理节、物理探索日和暑期女生项目。

项目成果

期刊论文数量（11）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

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