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arXiv 1202.4112cond-mat.supr-con
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CeCu2Si2的磁驱动超导电性

Magnetically driven superconductivity in CeCu2Si2

O. Stockert, J. Arndt, E. Faulhaber, C. Geibel, H. S. Jeevan, S. Kirchner, M. Loewenhaupt, K. Schmalzl, W. Schmidt, Q. Si, F. Steglich

摘要:

非常规超导的起源,包括高温和重费米子超导,仍然是一个有争议的问题。自旋激发而不是声子被认为是形成库珀对的原因。利用非弹性中子散射,我们提出了第一次在动量和能量空间中的超导和正常状态的CeCu2Si2的磁激发谱的深入研究。在超导态下观察到一个明显的自旋激发能隙。我们确定的超导状态下的磁交换能的降低,在一个相当大的量比超导凝聚能。我们的研究结果确定了反铁磁激发作为超导配对的主要驱动力,在这个原型的重费米子化合物位于反铁磁量子临界点附近。

英文摘要:

The origin of unconventional superconductivity, including high-temperature and heavy-fermion superconductivity, is still a matter of controversy. Spin excitations instead of phonons are thought to be responsible for the formation of Cooper pairs. Using inelastic neutron scattering, we present the first in-depth study of the magnetic excitation spectrum in momentum and energy space in the superconducting and the normal states of CeCu2Si2. A clear spin excitation gap is observed in the superconducting state. We determine a lowering of the magnetic exchange energy in the superconducting state, in an amount considerably larger than the superconducting condensation energy. Our findings identify the antiferromagnetic excitations as the major driving force for superconducting pairing in this prototypical heavy-fermion compound located near an antiferromagnetic quantum critical point.

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