Diverse Exotic Orders and Fermiology in Fe-Based Superconductors: A Unified Mechanism for B1g/B2g Nematicity in FeSe/(Cs,Rb)Fe2As2 and Smectic Order in BaFe2As2
Diverse Exotic Orders and Fermiology in Fe-Based Superconductors: A Unified Mechanism for B1g/B2g Nematicity in FeSe/(Cs,Rb)Fe2As2 and Smectic Order in BaFe2As2
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DOI：
10.3389/fphy.2022.915619
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发表时间：
2022-04
影响因子：
3.1
通讯作者：
S. Onari;H. Kontani
中科院分区：
文献类型：
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作者：
S. Onari;H. Kontani
铁基超导体中丰富的向列相/近晶有序是强关联电子系统中一个重要的悬而未决的问题。在过去的十年里，人们一直在调查对这些订单的统一理解。在本研究中，我们解释了FeSe_1BaFe_2As_2(A=Cs，Rb)中的B1G对称向列相转变、−_2As_2(A=Cs，Rb)中的B_2G对称向列相转变以及BaFe_2As_2中的近晶态。通过发展密度波动方程，我们研究了自旋涨落之间的量子干涉机制。观察到的丰富的向列相/近晶有序的种类自然地被理解在这个机制中。向列相/近晶相有序度取决于每个化合物的费米面的特征形状和拓扑。1)在FeSe_1的−_xTex(ND=6.0时)中，每个F_s都很小，Dxy轨道空穴口袋位于费米能级以下。在这种情况下，三个dxz、dyz和dxy轨道上的小自旋涨落共同导致了没有磁化的B1G向列相(Q=0)有序。在向列相转变温度(TS)以下的实验Lifshitz转变是自然复制的。2)在BaFe_2As_2(ND=6.0)中，在M点附近出现了DXY轨道空穴，每个空穴都较大。由于DXY轨道嵌套引起的强烈自旋涨落导致B1G向列相(Q=0)和近晶相[Q=(0，π)]有序，并且后者的转变温度(T*∼170K)超过了前者(TS∼140K)。3)在重空穴掺杂的AFe2As2(Nd=5.5)中，由于空穴掺杂，出现了较大的Dxy轨道空穴和四个微小的Dirac空穴。由于相同的干涉机制，在DXY轨道空穴口袋上出现了B2G向列键顺序。在铁基超导体已有的基础上，本顺磁非干涉机制提供了一个统一的解释，解释了为什么铁基超导体中的向列相/近晶相的种类如此丰富。
A rich variety of nematic/smectic orders in Fe-based superconductors is an important unsolved problem in strongly correlated electron systems. A unified understanding of these orders has been investigated for the last decade. In this study, we explain the B1g symmetry nematic transition in FeSe1−xTex, the B2g symmetry nematicity in AFe2As2 (A = Cs, Rb), and the smectic state in BaFe2As2 based on the same framework. We investigate the quantum interference mechanism between spin fluctuations by developing the density wave equation. The observed rich variety of nematic/smectic orders is naturally understood in this mechanism. The nematic/smectic orders depend on the characteristic shape and topology of the Fermi surface (FS) of each compound. 1) In FeSe1−xTex (nd = 6.0), each FS is very small and the dxy-orbital hole pocket is below the Fermi level. In this case, the small spin fluctuations on three dxz, dyz, and dxy orbitals cooperatively lead to the B1g nematic (q = 0) order without magnetization. The experimental Lifshitz transition below the nematic transition temperature (TS) is naturally reproduced. 2) In BaFe2As2 (nd = 6.0), the dxy-orbital hole pocket emerges around the M point, and each FS is relatively large. The strong spin fluctuations due to the dxy-orbital nesting give rise to the B1g nematic (q = 0) order and the smectic [q = (0, π)] order, and the latter transition temperature (T* ∼ 170K) exceeds the former one (TS ∼ 140K). 3) In heavily hole-doped AFe2As2 (nd = 5.5), the large dxy-orbital hole pocket and the four tiny Dirac pockets appear due to the hole-doping. The B2g nematic bond order emerges on the dxy-orbital hole pocket because of the same interference mechanism. The present paramagnon interference mechanism provides a unified explanation of why the variety of nematic/smectic orders in Fe-based superconductors is so rich, based on the well-established fermiology of Fe-based superconductors.