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arXiv 1405.7448cond-mat.supr-con
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铜氧化物超导体从低能到高能的动态自旋响应

Dynamical spin response in cuprate superconductors from low-energy to high-energy

Lulin Kuang, Yu Lan, Shiping Feng

摘要:

在动能驱动的超导机制框架下,研究了铜氧化物超导体从低能到高能的动态自旋响应。自旋自能是根据粒子-空穴通道和粒子-粒子通道中的集体载流子模式来计算的,并用于计算动态自旋结构因子。结果表明,在整个掺杂相图中存在阻尼但定义明确的色散自旋激发。特别地,超导态中的低能自旋激发具有沙漏形的色散,具有仅在超导态中出现的公度共振,而低能非公度自旋涨落可以持续到正常态。另一方面,超导态中的高能自旋激发保持大致恒定的能量作为掺杂的函数,其光谱权重和色散关系与相应的正常态中的光谱权重和色散关系相当。该理论还表明,铜氧化物超导体中不寻常的磁关联可以完全归因于自旋自能效应,自旋自能效应直接来自系统动能中的载流子-自旋相互作用。

英文摘要:

Within the framework of the kinetic energy driven superconducting mechanism, the dynamical spin response of cuprate superconductors is studied from low-energy to high-energy. The spin self-energy is evaluated explicitly in terms of the collective charge carrier modes in the particle-hole and particle-particle channels, and employed to calculate the dynamical spin structure factor. Our results show the existence of damped but well-defined dispersive spin excitations in the whole doping phase diagram. In particular, the low-energy spin excitations in the superconducting-state have an hour-glass-shaped dispersion, with commensurate resonance that appears in the superconducting-state only, while the low-energy incommensurate spin fluctuations can persist into the normal-state. The high-energy spin excitations in the superconducting-state on the other hand retain roughly constant energy as a function of doping, with spectral weights and dispersion relations comparable to those in the corresponding normal-state. The theory also shows that the unusual magnetic correlations in cuprate superconductors can be ascribed purely to the spin self-energy effects which arise directly from the charge carrier-spin interaction in the kinetic energy of the system.

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