Tetramer spin singlet instability in the fluorine-substituted pyrochlore superconducting system Cd2Re2O7-xFx
Tetramer spin singlet instability in the fluorine-substituted pyrochlore superconducting system Cd2Re2O7-xFx
复制标题
氟取代烧绿石超导体系 Cd2Re2O7-xFx 中四聚体自旋单线态不稳定性
DOI：
10.1088/0953-8984/28/35/355602
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
and Kazuyoshi Yoshimura
中科院分区：
文献类型：
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作者：
Yuya Haraguchi;Chishiro Michioka;Hiroaki Ueda;and Kazuyoshi Yoshimura
合成了含氟焦绿石稀土化合物Cd_2Re_2O_7-−_xF_x的多晶样品，并研究了它们的磁性、输运性质和结构性质。Re焦绿石网络中每个Re-4四面体交替膨胀和收缩的转变温度Ts1随着x的增加而降低，从x=0时的200K下降到x=0.5时的100K。低温相磁性和输运性质的强x相关性表明，结构相变的驱动力是四聚体自旋单态形成的涨落，以释放焦绿石晶格中的自旋受挫。此外，我们还发现了Cd_2Re_2O_7-−_xF_x的非常规超导性质，发现超导相变温度TC随x的增加而显著降低，表明缺陷的加入抑制了Coper对的凝聚。此外，尽管T_c减小，估计的零温上临界场仍超过泡利顺磁极限，并随x的增加而增大，因此，Cd_2Re_2O_7-−_xF_x是一种在自旋受阻晶格上巡回电子系统中实现的奇异超导体.
We synthesized polycrystalline samples of the fluorine-substituted pyrochlore rhenates Cd 2 Re 2 O 7− x F x, and investigated their magnetic, transport and structural properties. The transition temperature T s1, where each Re 4 tetrahedron in the Re pyrochlore network alternately expands and contracts, decreases with increasing x from 200 K at x= 0 to 100 K at x= 0.5. The strong x dependence of the magnetic and transport properties at the low-temperature phase indicates that the driving force of structural phase transition is fluctuations of the tetramer spin singlet formation in order to release the spin frustration in the pyrochlore lattice. Furthermore, we found unconventional superconducting properties in Cd 2 Re 2 O 7− x F x. It was found that the superconducting phase transition temperature T c markedly decreases with increasing x, suggesting that the addition of imperfection suppresses a condensation of Cooper-pair. In addition, the estimated upper critical field at zero temperature exceeds the Pauli paramagnetic limit and increases with increasing x in spite of the reduction of T c. Hence, Cd 2 Re 2 O 7− x F x is suggested to be an exotic superconductor realized in the itinerant electron systems on a spin frustrated lattice.