Fermi Surface with Dirac Fermions in CaFeAsF Determined via Quantum Oscillation Measurements
Fermi Surface with Dirac Fermions in CaFeAsF Determined via Quantum Oscillation Measurements
复制标题
通过量子振荡测量确定 CaFeAsF 中狄拉克费米子的费米表面
DOI：
10.1103/physrevx.8.011014
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发表时间：
2018
影响因子：
12.5
通讯作者：
Ikeda Hiroaki
中科院分区：
文献类型：
--
作者：
Terashima Taichi;Hirose Hishiro T.;Graf David;Ma Yonghui;Mu Gang;Hu Tao;Suzuki Katsuhiro;Uji Shinya;Ikeda Hiroaki
尽管1111型砷化铁保持着铁基超导体转变温度的纪录，但由于缺乏高质量的单晶，对其电子结构的研究还不多。在本研究中，我们通过量子振荡测量和能带结构计算，全面确定了1111砷化铁母体化合物CaFeAsF的反铁磁态下的费米面。确定的费米面由一对对称性相关的狄拉克电子柱和一个正常空穴柱组成。通过对量子振荡位相的分析，我们证明了电子柱携带的是一个非平凡的Berry相。载流子密度为Per Fe数量级。这种具有极小载流子密度的不寻常的金属状态是前面讨论的能带结构的拓扑特征的结果，该能带结构阻止了反铁磁间隙成为完整的间隙。我们还报道了近线性磁电阻和约30T以上的反常电阻率增加，后者可能与电子轨道的量子极限有关。有趣的是，在顺磁四方相()中，电阻率表现出非金属温度依赖关系，这可能暗示着一种非相干态。我们的研究提供了1111个母体化合物反铁磁态的费米面的详细信息，并为探索这些化合物中的狄拉克-费米子物理开辟了新的可能性。
Despite the fact that 1111-type iron arsenides hold the record transition temperature of iron-based superconductors, their electronic structures have not been studied much because of the lack of high-quality single crystals. In this study, we comprehensively determine the Fermi surface in the antiferromagnetic state of CaFeAsF, a 1111 iron-arsenide parent compound, by performing quantum oscillation measurements and band-structure calculations. The determined Fermi surface consists of a symmetry-related pair of Dirac electron cylinders and a normal hole cylinder. From analyses of quantum-oscillation phases, we demonstrate that the electron cylinders carry a nontrivial Berry phase. The carrier density is of the order ofper Fe. This unusual metallic state with the extremely small carrier density is a consequence of the previously discussed topological feature of the band structure which prevents the antiferromagnetic gap from being a full gap. We also report a nearly linear-in-magnetoresistance and an anomalous resistivity increase above about 30 T for, the latter of which is likely related to the quantum limit of the electron orbit. Intriguingly, the electrical resistivity exhibits a nonmetallic temperature dependence in the paramagnetic tetragonal phase (), which may suggest an incoherent state. Our study provides a detailed knowledge of the Fermi surface in the antiferromagnetic state of 1111 parent compounds and moreover opens up a new possibility to explore Dirac-fermion physics in those compounds.