Coherent Spectroscopy of Vortex-State Electrodynamics

高tc铜超导体的光学响应自从被发现以来，一直是人们密切研究的课题。从微波到红外线，一幅一致的反应图似乎终于出现了。然而，已经取得的理解主要局限于零磁场。提出的研究旨在深入了解涡旋状态下的光学响应，这是对磁场的响应。研究的重点是太赫兹频率范围，该频率范围对应于涡旋核中准粒子激发的间隙，是铜腔中涡旋动力学的关键频率范围。关键的实验工具是太赫兹时域光谱，这是测量介质在微波和红外光谱范围内宽带响应的最成功的方法。该技术通过求解近单周期皮秒电场脉冲的透射系数，直接测量了复响应函数。这些脉冲是通过使用飞秒锁模激光器产生和光电检测的。超导体的惊人特性是直流电阻的消失。然而，在零频率以上，超导体产生可测量的电阻，其特性是不同材料超导性的显著特征。本文研究了高温铜超导体在零外加磁场下从微波到可见光频率的电阻率。该项目研究了磁场下的基本和技术上的重要制度。该提案旨在全面了解铜超导体在大磁场存在下出现的“漩涡状态”的响应。研究的重点是光谱的太赫兹区域，这是铜酸盐的关键范围，并使用了一种强大的新的光谱工具，太赫兹时域光谱。广泛的高质量薄膜将被合成和研究。这一结果将测试和刺激理论工作，随着高温超导的非常规起源证据的出现，理论工作正在迅速发展。＊＊＊

9510353 Orenstein The optical response of high-Tc cuprate superconductors has been the subject of intense investigations since their discovery. It appears that a consistent picture of the responses, from microwave to infrared is finally emerging. However, the understanding that has been achieved is largely confined to zero magnetic field. The proposed research seeks to develop a thorough understanding of the optical response in the vortex-state which arises in response to magnetic field. The study focuses on the terahertz frequency range, which is the crucial one for vortex dynamics in the cuprates because it corresponds to the gap for quasi particle excitations in the vortex core. The key experimental tool is terahertz time-domain spectroscopy, which is the most successful approach to measuring broad band response of the media in the spectral range between the microwave and infra-red domains. In this technique the complex response function is measured directly by resolving the transmission coefficient of nearly-single-cycle picosecond electric field pulses. These pulses are generated and detected optoelectronically through the use of a femtosecond mode- locked laser. %%% The spectacular property of superconductors is the vanishing of the dc resistance. However, above zero frequency, superconductors develop measurable resistance, whose properties are a distinguishing feature of superconductivity in different materials. The resistivity of high temperature cuprate superconductors in zero applied magnetic field, from microwave to visible frequencies, has been studied intensively. This project investigates the fundamentally and technologically important regime of under magnetic field. The proposal seeks to develop a thorough understanding of the response of cuprate superconductors in the "vortex state" which arises in the presence of large magnetic field. The research focus es on the terahertz region of the spectrum, which is the crucial range for the cuprates, and uses a powerful new spectroscopic tool, terahertz time-domain spectroscopy. A broad range of high quality films will be synthesized and investigated . The results will test and stimulate theoretical work, which is evolving rapidly as evidence emerges for unconventional origins of superconductivity in HTS. ***