Search for quantum criticality and its control by precise microwave broadband spectroscopy

通过精确微波宽带光谱寻找量子临界性及其控制

• 批准号: 17340102
• 负责人: MAEDA Atsutaka
• 金额: $ 10.39万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2005
• 资助国家: 日本
• 起止时间: 2005 至 2007
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-17340102/
• 关键词: THz spectroscopy; complex conductivity; microwave conductivity; pseudogap; superconductivity fluctuation; time domain spectroscopy; cuprate high Tc superconductors; quantum critical point; THzスペクトロスコピー; ミリ波電気伝導度; ラットリング運動; パイロクロア型酸化物超伝導体; ミリ波

We studied the critical charge dynamics of the superconducting to the normal-state transition for La2-xSrxCuO4 (LSCO) with a wide range of the Sr concentration by measuring the frequency dependent excess complex microwave conductivity (superconducting fluctuations). By a dynamic scaling analysis of the data, we found the two-dimensional (2D)-XY critical dynamics for underdoped LSCO and the three dimensional (3D-XY) critical dynamics for optimally doped LSCO. Furthermore, we observed a two-dimensional unknown critical charge dynamics ("2D unknown") for overdoped thin films. Thus, it was found that the critical behavior in the phase diagram of LSCO is classified into the following three types: (i) 2D-XY for underdoped region, (ii) 3D-XY for optimally doped region, and (iii) 2D-"U" for overdoped region. Thus, the dimensionality in the critical charge dynamics is changed twice with hole doping. We discuss possible origins of such anomalous dimensional crossovers with hole doping, including an interpretation based on the possible existence of a hidden quantum critical point near the optimally doped region. Correct theoretical model for high-Tc superconductivity should explain all of these behaviors. (Not that electron doped cuprates were found to show 3D-XY features. for all carrier dopings)We also performed conductivity measurements in THz region, and found that the upper limit of superconductivity fluctuation is at most twice the zero resistance temperature. This is in good agreement with the microwave results, and suggests that the interpretation that the Nernst signal is the representation of superconductivity fluctuation is wrong. We found another characteristic temperature where scattering time becomes longer. This temperature agrees well with the pseudogap onset temperature observed in photoemission studies.

通过测量随频率变化的过剩复微波电导率（超导涨落），研究了Sr浓度变化范围较宽的La 2-xSrxCuO 4（LSCO）超导态向正常态转变的临界电荷动力学。通过对实验数据的动力学标度分析，我们发现了欠掺杂LSCO的二维（2D）-XY临界动力学和最佳掺杂LSCO的三维（3D-XY）临界动力学。此外，我们观察到一个二维未知的临界电荷动力学（“二维未知”）过掺杂薄膜。因此，发现LSCO相图中的临界行为分为以下三种类型：（i）欠掺杂区的2D-XY，（ii）最佳掺杂区的3D-XY，和（iii）过掺杂区的2D-“U”。因此，在临界电荷动力学的维数改变了两次与空穴掺杂。我们讨论了这种异常的尺寸交叉与空穴掺杂的可能起源，包括基于最佳掺杂区域附近可能存在的隐藏量子临界点的解释。正确的高温超导理论模型可以解释所有这些行为。(Not发现电子掺杂的铜氧化物显示出3D-XY特征。我们还在THz区进行了电导率测量，发现超导涨落的上限最多为零电阻温度的两倍。这与微波测量结果相一致，表明能斯特信号是超导涨落的代表的解释是错误的。我们发现了另一个特征温度，散射时间变得更长。这个温度与光电子能谱研究中观察到的赝能隙起始温度吻合得很好。

项目成果

La_<2-x>Sr_xCuO_4薄膜における擬ギャップ領域のテラヘルツ複素伝導度測定

La_<2-x>Sr_xCuO_4薄膜赝能隙区太赫兹复电导率测量

• 发表时间: 2008
• 作者: 中村大輔;今井良宗;前田京剛;塚田一郎
• 通讯作者: 塚田一郎

Challenges to high-Tc superconductivity in cuprateds by exploring condensate properties

通过探索凝聚态特性对铜酸盐高温超导性提出挑战

• 发表时间: 2008
• 期刊: J. Phys. Conf. Ser. 108
• 作者: Maeda;A.
• 通讯作者: A.

Direct observation of rectified motion of vortices by Lorentz microscopy

通过洛伦兹显微镜直接观察涡流的校正运动

• 发表时间: 2006
• 期刊: Pramana-Journal of Physics 66
• 作者: R.Inoue;Y.Odate;E.Tanabe;H.Kitano;A.Maeda;H.Kitano;Y.Togawa
• 通讯作者: Y.Togawa

Nanoscale friction : kinetic friction on magnetic flux quanta and charge-density waves

纳米级摩擦：磁通量量子和电荷密度波的动摩擦

• 发表时间: 2005
• 期刊: Phys.Rev.Lett. 94
• 作者: R.Inoue;Y.Odate;E.Tanabe;H.Kitano;A.Maeda;H.Kitano;Y.Togawa;A. Maeda;T. Ohashi;A.Maeda;T.Ohashi;A.Maeda
• 通讯作者: A.Maeda

Magnetic field effect on the superconductivity fluctuation of cuprates, LSCO and LCCO measured by microwave broadband technique

微波宽带技术测量磁场对铜酸盐、LSCO和LCCO超导涨落的影响

• 发表时间: 2007
• 作者: Maeda;A.;A. Maeda Phase;A. Maeda;A. Maeda;A. Maeda;A. Maeda;大橋健良;大橋健良;A. Maeda;A. Maeda
• 通讯作者: A. Maeda