Orbital-dependent pairing effects in the nuclear spin–lattice relaxation rate of Sr2RuO4
Orbital-dependent pairing effects in the nuclear spin–lattice relaxation rate of Sr2RuO4
复制标题
Sr2RuO4 核自旋-晶格弛豫率中的轨道依赖性配对效应
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
Balazs L. Gyorffy
中科院分区：
文献类型：
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作者：
K. Wysokiński;J. Annett;Balazs L. Gyorffy
p波手性超导体Sr2RuO4是一种准二维、高度各向异性的系统，具有跨越费米能的三个能带。在与温度相关的物理性质中观察到低温幂律行为，包括比热、穿透深度和核磁共振弛豫率，这与准粒子间隙中存在一线节点一致。然而，由于多能带或轨道相关配对可能产生温度依赖性，这些实验的解释变得复杂。在本文中，我们基于具有唯象耦合常数的现实轨道特定、三轨道、三维模型计算了核磁共振弛豫率 1/T1。该模型导致费米能级 γ 片上具有手性无带隙有序参数的基态，并且在其余两个片上具有节点。我们的结果与现有的实验 101Ru NQR 数据相比较，显示弛豫率为 1/T1∼T3，并且在 Tc 以下没有可见的 Hebel-Slichter 样峰。另一方面，弛豫率的对角 dxy 轨道投影分量显示出更复杂的行为，包括低于 Tc 的 Hebel-Slichter 状峰。我们推测这些轨道依赖性可能与该材料中 17O 和 101Ru 核的自旋弛豫率之间观察到的差异有关。
The p-wave chiral superconductor Sr2RuO4 is a quasi-two-dimensional, highly anisotropic system with three bands crossing the Fermi energy. Low temperature power law behaviour is observed in temperature-dependent physical properties, including specific heat, penetration depth and NMR relaxation rate, which is consistent with the existence of a line of nodes in the quasiparticle gap. However, the interpretation of these experiments is complicated by possible temperature dependences arising from the multi-band or orbital-dependent paring. In this paper we have calculated the NMR relaxation rate 1/T1 on the basis of a realistic orbital-specific, three-orbital, three-dimensional model with phenomenological coupling constants. The model leads to the ground state with chiral–gapless order parameter on the γ sheet of the Fermi level and with nodes on the remaining two sheets. Our results compare well with existing experimental 101Ru NQR data showing a relaxation rate 1/T1∼T3 and no visible Hebel–Slichter-like peak below Tc. On the other hand, the diagonal dxy orbital projected components of the relaxation rate show a more complex behaviour, including a Hebel–Slichter-like peak below Tc. We speculate that these orbital dependences might be related to the differences observed between spin relaxation rates for 17O and 101Ru nuclei in this material.