CAREER: Anisotropic Femtosecond Spectroscopy of High-Tc Superconductors

职业：高温超导体的各向异性飞秒光谱

• 批准号: 9734131
• 负责人: W. Andreas Schroeder
• 金额: $ 30万
• 依托单位: University of Illinois at Chicago
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-03-15 至 2003-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9734131&HistoricalAwards=false
• 关键词: CAREER; Anisotropic; Femtosecond; Spectroscopy; Tc

9734131 Schroeder This is a CAREER Award which will investigate the fundamental properties of intrinsically anisotropic high-TC cuprate superconductors using powerful, sophisticated, and polarization-sensitive time-resolved ultrafast spectroscopic techniques. An ultrabroadband femtosecond terahertz (THz) probe pulse (generated by optical rectification of a 50fs optical pulse) will be used to spectrally time resolve the far-infrared transient response of high-TC superconductors induced by an optical pump pulse through the change in the reflectivity produced by the perturbed complex conductivity. Since the spectral extent of the linearly polarized THz probe pulse includes the superconducting gap 2A, this technique will be used to monitor directly the optically-induced perturbations to the anisotropic order parameter A, the pseudogap in under-doped materials, and transient inter- and intra-plane coupling between Cu-O layers and chains using untwinned Yttrium- and Barium-based cuprate crystals. In addition, to aid the understanding of the time-resolved THz spectra, two-photon excited-state angle-resolved photoemission spectroscopy will be employed to determine the relevant characteristics (lifetime and momentum) of the optically-coupled unoccupied states above the Fermi level. All measurements will be performed as a function of TITC to elucidate temperature dependencies. The results from these carefully designed ultrafast spectroscopic measurements should have a great impact on our understanding of the unique properties of high-TC superconductors in a manner parallel to that provided by similar femtosecond optical techniques in semiconductor physics. The educational component will involve both undergraduate physics majors and students from Chicago area high schools in research in the investigators laboratory that is connected to the goals of the project. %%% This is a CAREER Award which uses sophisticated optical methods to study high temperature superconductor s. The discovery in 1986 of copper-oxide-based ceramic materials, which exhibit zero electrical resistance at liquid nitrogen (-3 F) (rather than liquid helium (-450 F)) temperatures, has ignited technological interest in superconductivity as a means of dramatically reducing energy distribution costs, developing efficient high-speed levitating transportation, and making ultrafast electronic switches. However, despite a decade of exciting research into the properties of high-temperature superconductors (HTSCs), a definitive experiment leading to a clear understanding of the physical mechanism responsible for superconductivity in these unique materials has not been forthcoming. The goal of this research program is to exploit the sub-picosecond (shorter than one-thousand-billionth of a second) temporal resolution provided by today's laser technology to study the fundamental physical processes occurring in HTSCs. Specifically, ultrashort pulses of far-infrared radiation will be used to monitor the response of HTSCs in an effort to time-resolve the mechanism responsible for superconductivity in these ceramic materials. These ultrafast optical investigations will open a new regime of study for superconductivity in which radiation is used to monitor directly the electronic dynamics of the superconducting state. The results from these novel spectroscopic studies should have a significant impact on our understanding of the unique properties of HTSCs which, in turn, may lead to the development of superconductors operating at even higher temperatures. Indeed, similar ultrafast optical techniques have already improved our understanding and design of everyday semiconductor devices. The educational component will involve both undergraduate physics majors and students from Chicago area high schools in research in the investigators laboratory that is connected to the goals of the project. ***

小行星9734131 这是一个CAREER奖，将使用强大，复杂和偏振敏感的时间分辨超快光谱技术研究本质各向异性高TC铜酸盐超导体的基本特性。超宽带飞秒太赫兹（THz）探测脉冲（由50 fs光脉冲的光学整流产生）将用于通过反射率的变化来光谱时间分辨由光泵脉冲引起的高TC超导体的远红外瞬态响应。由扰动的复电导率。由于线偏振太赫兹探测脉冲的光谱范围包括超导间隙2A，因此该技术将用于直接监测各向异性序参数A的光致扰动、欠掺杂材料中的赝间隙以及使用非孪晶钇和钡基铜酸盐晶体的Cu-O层和链之间的瞬态面间和面内耦合。此外，为了帮助理解的时间分辨太赫兹光谱，双光子激发态角分辨光电子能谱将被用来确定费米能级以上的光耦合未占态的相关特性（寿命和动量）。 所有测量将作为TTC的函数进行，以阐明温度依赖性。这些精心设计的超快光谱测量的结果应该对我们理解高TC超导体的独特性质产生重大影响，其方式与半导体物理学中类似的飞秒光学技术所提供的方式平行。教育部分将涉及本科物理专业和学生从芝加哥地区的高中在研究人员实验室，是连接到该项目的目标。 这是一个使用先进的光学方法来研究高温超导体的职业奖。1986年发现的氧化铜基陶瓷材料在液氮（-3 F）（而不是液氦（-450 F））温度下表现出零电阻，引发了对超导性的技术兴趣，作为一种显著降低能量分配成本的手段，开发高效的高速悬浮运输，并制造超快电子开关。然而，尽管对高温超导体（HTSC）的性质进行了十年的令人兴奋的研究，但导致对这些独特材料中超导性的物理机制的明确理解的决定性实验尚未到来。该研究计划的目标是利用当今激光技术提供的亚皮秒（短于十亿分之一秒）时间分辨率来研究HTSC中发生的基本物理过程。具体来说，远红外辐射的超短脉冲将用于监测HTSC的响应，以努力在时间上解决这些陶瓷材料中超导性的机制。这些超快光学研究将为超导性的研究开辟一个新的领域，其中辐射被用来直接监测超导态的电子动力学。这些新的光谱研究的结果应该对我们理解HTSC的独特性质产生重大影响，这反过来可能导致在更高温度下工作的超导体的发展。事实上，类似的超快光学技术已经改善了我们对日常半导体器件的理解和设计。教育部分将涉及本科物理专业和学生从芝加哥地区的高中在研究人员实验室，是连接到该项目的目标。 ***