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arXiv 0705.3988cond-mat.supr-concond-mat.str-el
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低于Tc的高温超导体的热导率理论:空穴掺杂和电子掺杂体系的比较

Theory of Thermal Conductivity in High-Tc Superconductors below Tc: Comparison between Hole-Doped and Electron-Doped Systems

Hideyuki Hara, Hiroshi Kontani

摘要:

在空穴掺杂的高Tc超导体中,热导率在低于Tc时急剧增加,这被认为是节点间隙的标志。相比之下,热导率的这种相干峰在电子掺杂的化合物中是不可见的,这可以指示诸如(d+is)波状态的全带隙状态。为了解决这一问题,我们在哈伯德模型中采用波动交换(FLEX)近似研究了热导率,预言了d波节态在空穴掺杂和电子掺杂的化合物中均能实现.两种化合物的热导率的对比行为源于热/冷点结构的差异。一般情况下,只有当冷斑存在于节线上时,线结超导体的热导率才会出现显著的相干峰。

英文摘要:

In hole-doped high-Tc superconductors, thermal conductivity increases drastically just below Tc, which has been considered as a hallmark of a nodal gap. In contrast, such a coherence peak in thermal conductivity is not visible in electron-doped compounds, which may indicate a full-gap state such as a (d+is)-wave state. To settle this problem, we study the thermal conductivity in the Hubbard model using the fluctuation-exchange (FLEX) approximation, which predicts that the nodal d-wave state is realized in both hole-doped and electron-doped compounds. The contrasting behavior of thermal conductivity in both compounds originates from the differences in the hot/cold spot structure. In general, a prominent coherence peak in thermal conductivity appears in line-node superconductors only when the cold spot exists on the nodal line.

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