Theoretical Study of Exotic Superconductivity and Magnetism

奇异超导与磁性的理论研究

• 批准号: 04640369
• 负责人: MIYAKE Kazumasa
• 金额: $ 0.77万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04640369/
• 关键词: Cuprate superconductor; Nested Spin Fluctuations; Anomalous Metallic Phase; Normal State of Cuprates; Itinerant-Localized Duality; de Haas-van Alphen Effect in Superconducting State; Anisotropic Superconductivity; 型にはまらない超伝導; スピンゆらぎ; 銅酸化物超伝導; 超伝

On the basis of analysis of the superconducting flusctuation effect on the NMR relaxation rate, which shows drastic decrease just above the transition temperature, it was found that the symmetry of the pairing of cuprate superconductor is favorable for d_<xy>pairing among the d-symmetry. We have performed a calculation for hole-number dependence of the transition temperature by taking into account the effect of the off-site repulsion U_<pd> between electrons on copper and oxygen. In the calculation, we follow the RPA treatment of U_<pd> after the strong on-site repulsion U_d is renormalized into the quasi-particle state. the results are in qualitative agreement with experiments. It was also found that the off-site repulsion U_<pd> easily destroy the d_<x2-y2> pairing.On the basis of research on the properties of antiferromagnetic nested spin fluctuations in 2D metals, it was found that the anomalous metallic phase observed in the normal state of cuprates, with aspects such as "spin gap … More " and "spin-charge separation", can be explained in a unified way as an effect of the mode-mode coupling of spin fluctuations on the itinerant-localized duality picuture when the renormalized Fermi surface is technically nested.In order to investigate the property of the de Haas-van Alphen (dHvA) effect in superconducting state, we have carried out the calculations adopting the Landau orbit as a basis of the single particle state. As a result, it turned out that the dHvA oscillations can be observed only in a very narrow region near the upper critical field if the symmetry of the pairing is isotropic s wave. This in turn shows that the anisotropic superconductivity, with the gap vanishing on the point (s) or line (s) on the Fermi surface, should be considered in the case the dHvA oscillations are observed well below the upper critical field.We have discussed the problem of the crossover between wavenumber-space pairing and real-space pairing being motivated by the fact that the cuprate superconductors, with very short coherence length of a few times the lattice constant, are expected to locate in the crossover region. The difficulty of the Nozieres & Schmitt-Rink theory applied to 2D case was analyzed critically. It was shown that its difficulty can be avoided when the supercounducting transition is treated in the Kosterlitz & Thouless formalism. Less

通过分析超导涨落对核磁共振弛豫率的影响，发现在转变温度以上时，核磁共振弛豫率急剧下降，发现铜酸盐超导体配对的对称性有利于d对称性中的d_<xy>配对。我们通过考虑电子对铜和氧之间的场外斥力 U_<pd> 的影响，计算了转变温度与空穴数的关系。在计算中，我们将强原位斥力U_d重整到准粒子态后对U_<pd>进行RPA处理。结果与实验定性一致。还发现异位斥力U_<pd>很容易破坏d_<x2-y2>配对。通过对二维金属中反铁磁嵌套自旋涨落性质的研究，发现在铜酸盐正常状态下观察到的反常金属相，在“自旋间隙”和“自旋电荷分离”等方面可以统一解释为 为了研究超导态下的德哈斯-范阿尔芬（dHvA）效应的性质，我们采用朗道轨道作为单粒子态的基础进行了计算。结果表明，如果配对的对称性是各向同性 s 波，则只能在上临界场附近的非常狭窄的区域中观察到 dHvA 振荡。这反过来表明，在远低于上临界场的情况下观察到 dHvA 振荡时，应考虑各向异性超导性，即费米面上的点或线上的间隙消失。我们讨论了波数空间配对和实空间配对之间的交叉问题，其动机是铜酸盐超导体的相干长度非常短 晶格常数的几倍，预计位于交叉区域。批判性地分析了Nozieres & Schmitt-Rink理论应用于二维情况的困难。结果表明，用Kosterlitz & Thouless形式主义来处理超导转变可以避免这个困难。较少的

项目成果

K.Miyake: "Spin-Charge Separation Aspect and Anomalies of Hall Constant in 2D Metals with Technically Nested Fermi Surface" Physica C. 235-240. 2237-2238 (1994)

K.Miyake：“具有技术嵌套费米表面的二维金属中的自旋电荷分离方面和霍尔常数的异常”Physica C.235-240。

T.Tsuji, O.Narikiyo and K.Miyake: "Doping Dependence of Hole-Number Distribution on CuO_2 Plane and Superconducting Transition Temperature of High-T_c Cuprates by d_<xy>-Pairing Scenario" Physica C. Vol.244 (in press). (1995)

T.Tsuji、O.Narikiyo 和 K.Miyake：“通过 d_<xy>-配对场景对 CuO_2 平面上的孔数分布和高 T_c 铜氧化物超导转变温度的掺杂依赖性”Physica C. Vol.244（印刷中）

A.Tokumitu and K.Miyake: "Crossover from BCS to Local Pair Superconductivity in Two Dimensions" Physica C. 235-240. 2367-2368 (1994)

A.Tokumitu 和 K.Miyake：“从 BCS 到二维局部对超导的交叉”Physica C. 235-240。

K.Miyake: "Aspect of Spin-Charge Separation due to Antiferromagnetic Spin Fluctuations in Technically Nested 2D Metals" J.Phys.Soc.Jpn. 63. 2042-2046 (1994)

K.Miyake：“技术嵌套二维金属中反铁磁自旋涨落导致的自旋电荷分离方面”J.Phys.Soc.Jpn。

K.Miyake and O.Narikyo: "Itinerant-Localized Duality Picture of spin Fluctuations in High T_c Cuprates : I.Nested Spin-Fluctuation Theory" J.Phys.soc.Jpn.Vol.63. 3821-3837 (1994)

K.Miyake 和 O.Narikyo：“高 T_c Cuprates 中自旋波动的流动局域对偶图：I.嵌套自旋波动理论”J.Phys.soc.Jpn.Vol.63。