Enhanced low-energy magnetic excitations evidencing the Cu-induced localization in the Fe-based superconductor Fe0.98</mml
Enhanced low-energy magnetic excitations evidencing the Cu-induced localization in the Fe-based superconductor Fe0.98</mml
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DOI：
10.1103/physrevb.105.245129
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发表时间：
2022-06
影响因子：
3.7
通讯作者：
Jinghui Wang;Song Bao;Yanyan Shangguan;Zhengwei Cai;Yuan Gan;Shichao Li;K. Ran;Zhen Ma;
中科院分区：
文献类型：
--
作者：
Jinghui Wang;Song Bao;Yanyan Shangguan;Zhengwei Cai;Yuan Gan;Shichao Li;K. Ran;Zhen Ma;
我们对最佳掺杂的Fe${0.98}$Te${0.5}$Se${0.5}$和10% Cu掺杂的Fe${0.88}$Cu${0.1}$Te ${0.5}$Se ${0.5}$进行了非弹性中子散射测量，研究了在300 meV以下的整个能量范围内替代效应对自旋激发的影响。它被发现，取代Cu的Fe增强了低能量的自旋激发（$\le $100毫电子伏），特别是在（0.5，0.5）点附近，并留下了完整的高能量的磁激发。与自旋为1/2的Cu将稀释具有较大自旋的Fe所贡献的磁矩的预期相反，我们发现10%Cu掺杂将有效波动磁矩从2.85增大到3.13 $\mu_{\rm B}$/Fe，尽管在（0.5，0.5）和（0.5，0）附近没有长程或短程磁序。掺杂10%Cu的铁基超导体在绝缘状态下存在增强的磁激发，表明磁激发中一定有局域磁矩的贡献，反映了铁基超导体磁性的双重性。我们把这种替代效应归因于Cu掺杂引起的巡游电子的局域化。这些结果也表明，铜掺杂不作为电子供体在刚性带移模型，但更多的散射中心，本地化系统。
We have performed inelastic neutron scattering measurements on optimally-doped Fe$_{0.98}$Te$_{0.5}$Se$_{0.5}$ and 10% Cu-doped Fe$_{0.88}$Cu$_{0.1}$Te$_{0.5}$Se$_{0.5}$ to investigate the substitution effects on the spin excitations in the whole energy range up to 300 meV. It is found that substitution of Cu for Fe enhances the low-energy spin excitations ($\le$ 100 meV), especially around the (0.5, 0.5) point, and leaves the high-energy magnetic excitations intact. In contrast to the expectation that Cu with spin 1/2 will dilute the magnetic moments contributed by Fe with a larger spin, we find that the 10% Cu doping enlarges the effective fluctuating moment from 2.85 to 3.13 $\mu_{\rm B}$/Fe, although there is no long- or short-range magnetic order around (0.5, 0.5) and (0.5, 0). The presence of enhanced magnetic excitations in the 10% Cu doped sample which is in the insulating state indicates that the magnetic excitations must have some contributions from the local moments, reflecting the dual nature of the magnetism in iron-based superconductors. We attribute the substitution effects to the localization of the itinerant electrons induced by Cu dopants. These results also indicate that the Cu doping does not act as electron donor as in a rigid-band shift model, but more as scattering centers that localize the system.