Dynamics of low dimensional quantum spin systems and effects of carrier doping.

低维量子自旋系统的动力学和载流子掺杂的影响。

• 批准号: 10304027
• 负责人: TAKIGAWA Masashi
• 金额: $ 23.55万
• 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 (A)
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10304027/
• 关键词: Quantum Spin System; Nuclear Magnetic Resonance; Carrier Doping; Spin Gap; Low Dimensionality; 梯子格子; 近藤絶縁体; ホールドープ; 電荷ゆらぎ; 電荷凍結; 近藤半導体; スピン拡散; 高温超伝導

Since the high temperature superconductivity was discovered in 1986, various attempts were made to dope carriers into low dimensional quantum spin systems, which are the Mott-insulators and to find superconductivity. In such a trend of research, the first objectives of this project was set to clarify the dynamics of the low dimensional quantum spin systems from a microscopic point of view using nuclear magnetic resonance as the principal tool. Second objective was to understand the change in magnetic dynamics upon elemental substitution or doping carriers or impurities. The former was achieved by the experiments on the hole-doped spin-ladder materials and the two-dimensional orthogonal dimer spin systems, which yielded variety of different behavior of spin excitations for the singket ground state. Concerning the latter, experiments on hole-doped ladder materials have shown that interaction between carriers and the magnetic excitations induces paring of holes. The thermally depaired carriers are shown to cause significant damping of magnetic excitations. Furthermore, extremely slow charge fluctuations associated with partial charge ordering were observed in a few quasi-one-dimensional conducting systems. On the other hand, in Kondo insulators, which is another example of spin gap material, we found that local moments are induced near impurities similar to the case of quantum spin systems.

自1986年发现高温超导以来，人们进行了各种尝试将载流子掺杂到低维量子自旋系统（莫特绝缘体）中并寻找超导性。在这样的研​​究趋势下，该项目的首要目标是以核磁共振为主要工具，从微观角度阐明低维量子自旋系统的动力学。第二个目标是了解元素替代或掺杂载体或杂质时磁动力学的变化。前者是通过空穴掺杂自旋梯材料和二维正交二聚体自旋系统的实验实现的，产生了单基态自旋激发的各种不同行为。关于后者，空穴掺杂梯形材料的实验表明，载流子和磁激发之间的相互作用会引起空穴配对。热脱合载体被证明会导致磁激励的显着阻尼。此外，在一些准一维导电系统中观察到与部分电荷排序相关的极慢的电荷波动。另一方面，在自旋间隙材料的另一个例子近藤绝缘体中，我们发现在杂质附近会产生局部矩，类似于量子自旋系统的情况。

项目成果

K. Ohwada: "Devil's Staicase-Type Phase Transition in NaV_20_5 under High Pressure"Phys. Rev. Lett.. 87. 086402-1-4 (2001)

K. Ohwada：“高压下 NaV_20_5 中的魔鬼型相变”Phys。

O. Vyaselev: "Lattice Distortion and First Order Transition in TlCuCl_3"Proceedings of Japanese-French Seminar. (in press).

O. Vyaselev：“TlCuCl_3 中的晶格畸变和一阶跃迁”日法研讨会论文集。

陰山 洋: "Exact Dimen Ground State and Quantized Magnelization Plateaus in the Two-Dimensional Spin System SrCn_2(Bo_3)_2"The Physical Review Letters. 82・15. 3168-3171 (1999)

Hiroshi Kageyama：“二维自旋系统 SrCn_2(Bo_3)_2 中的精确维门基态和量子化磁化平台”物理评论快报 82・15 (1999)。

D.Akahoshi: "Oxygen Nonstoichiometry, Structures, and Physical Properties of YbaCo_2O_<5+x>(0.00 x 0.52)"J. Solid State Chem.. 156. 355-363 (2001)

D.Akahoshi：“YbaCo_2O_<5 x>(0.00 x 0.52) 的氧非化学计量、结构和物理性质”J。

0.Vyaselev: "Cd and Re NMR/NQR in Pyrochlore Compound Cd_2Re_2O_7"J. Phys. Chem. Solids. (印刷中).

0.Vyaselev：“烧绿石化合物 Cd_2Re_2O_7 中的 Cd 和 Re NMR/NQR”J Chem。