arXiv 1402.06162014-02-04cond-mat.supr-con

强Pauli限制准一维超导体中Fulde-Ferrell-Larkin-Ovchinnikov态的维度交叉

Dimensional Crossover of the Fulde-Ferrell-Larkin-Ovchinnikov State in Strongly Pauli-Limited Quasi-One-Dimensional Superconductors

Nobumi Miyawaki, Hiroshi Shimahara

备注：: 7 pages, 6 figures, jpsj3.cls
发表信息：: J. Phys. Soc. Jpn. Vol.83, 024703 (2014)
DOI：: 10.7566/JPSJ.83.024703

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摘要：

研究了准一维s波和d波超导体中的Fulde-Ferrell-Larkin-Ovchinnikov（FFLO）态，特别注意了费米面各向异性的影响.上临界场$H_{c2}(T)$被发现表现出定性不同的行为取决于跳跃能量$t_b/t_a$和FFLO调制矢量q的方向的比率，其中$t_a$和$t_b$是链内和链间跳跃能量，分别。特别地，当$t_b/t_a < 0.1$和$\mathbf{q} \parallel \mathbf{a}$，我们发现了一个新的维度交叉的$H_{c2}(T)$从一维到二维，其中a是最导电链的晶格矢量。就在三临界温度$T^*$以下，上临界场$H_{c2}(T)$像一维系统一样急剧增加，但当温度降低时，$H_{c2}(T)$的增加率减小，并出现肩部。在$T = 0$附近，$H_{c2}(T)$显示二维系统中FFLO状态的典型行为，即，在$T = 0$的有限域中出现好转。当$\mathbf{q}$和$\mathbf{a}$之间的角度较大时，上临界场曲线在低温下向上凸起，如在三维系统中一样，但幅度远大于三维各向同性系统的幅度。对于$t_b/t_a > 0.15$，除了在$0.2 > t_b/t_a > 0.15$范围内的轻微肩部外，上临界场表现出二维行为。对于s波和d波配对，$\mathbf{q} \parallel \mathbf{a}$的上临界场都是最大的，而对于$\mathbf{q} \perp \mathbf{a}$，它仅略大于泡利顺磁极限。本文还讨论了上述结果与有机超导体${\rm (TMTSF)_2ClO_4}$的相关性。

英文摘要：

The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is examined in quasi-one-dimensional s-wave and d-wave superconductors with particular attention paid to the effect of the Fermi-surface anisotropy. The upper critical field $H_{c2}(T)$ is found to exhibit a qualitatively different behavior depending on the ratio of the hopping energies $t_b/t_a$ and the direction of the FFLO modulation vector q, where $t_a$ and $t_b$ are the intra- and interchain hopping energies, respectively. In particular, when $t_b/t_a < 0.1$ and $\mathbf{q} \parallel \mathbf{a}$, we find a novel dimensional crossover of $H_{c2}(T)$ from one dimension to two dimensions, where a is the lattice vector of the most conductive chain. Just below the tricritical temperature $T^*$, the upper critical field $H_{c2}(T)$ increases steeply as in one-dimensional systems, but when the temperature decreases, the rate of increase in $H_{c2}(T)$ diminishes and a shoulder appears. Near $T = 0$, $H_{c2}(T)$ shows a behavior typical of the FFLO state in two-dimensional systems, i.e., an upturn with a finite field at $T = 0$. When the angle between $\mathbf{q}$ and $\mathbf{a}$ is large, the upper critical field curve is convex upward at low temperatures, as in three-dimensional systems, but the magnitude is much larger than that of a three-dimensional isotropic system. For $t_b/t_a > 0.15$, the upper critical fields exhibit a two-dimensional behavior, except for a slight shoulder in the range of $0.2 > t_b/t_a > 0.15$. The upper critical field is maximum for $\mathbf{q} \parallel \mathbf{a}$ both for s-wave and d-wave pairings, while it is only slightly larger than the Pauli paramagnetic limit for $\mathbf{q} \perp \mathbf{a}$. The relevance of the present results to the organic superconductor ${\rm (TMTSF)_2ClO_4}$ is discussed.

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