Density Wave State in New α-Type Organic Conductor, α-(BEDT-TTF)2MHg(XCN)4 (M = NH4, X = Se): A Key Material for Universal Phase Diagram of X = S and X = Se Systems
Density Wave State in New α-Type Organic Conductor, α-(BEDT-TTF)2MHg(XCN)4 (M = NH4, X = Se): A Key Material for Universal Phase Diagram of X = S and X = Se Systems
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新型α型有机导体α-(BEDT-TTF)2MHg(XCN)4 (M = NH4, X = Se)中的密度波态：X = S和X = Se系统通用相图的关键材料
DOI：
10.1021/acs.jpcc.8b08912
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Kawamoto Atsushi
中科院分区：
文献类型：
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作者：
Ohnuma Akihiro;Taniguchi Hiromi;Takahashi Yukihiro;Kawamoto Atsushi
α-（BEDT-TTF）_2MHg（SCN）_4是一类有机导体，在低温下，M = Tl，K和Rb盐呈现密度波（DW）态，M = NH_4盐呈现超导（SC）态。相比之下，α-（BEDT-TTF）2 MHg（SeCN）4没有相变，并在低温下保持其金属特性。由于没有α-（BEDT-TTF）2 Hg（SeCN）4盐显示DW或SC状态，因此不清楚α-（BEDT-TTF）2 Hg（SeCN）4体系是否可以通过与α-（BEDT-TTF）2 Hg（SCN）4相同的相图来理解。在此，我们成功地合成了一种关键材料α-（BEDT-TTF）2NH 4 Hg（SeCN）4，并测定了其晶体结构。其电导率和自旋磁化率的温度依赖性表明其在低温下处于DW态，表明α-（BEDT-TTF）2 MHg（SeCN）4体系与α-（BEDT-TTF）2 MHg（SCN）4体系存在联系.从所建立的相图中，我们发现晶体学上独立的A和B分子之间的二面角ΘB以及A和C分子之间的二面角ΘC是良好的调谐参数，如在θ型BEDT-TTF盐中。在θB-Θ C图中，SC盐位于大Θ带小Θ C区，而金属盐位于小Θ带大Θ C区。DW盐位于中间Θ带Θ C区域。它们在ΘB-Θ C图中的位置与基态之间的关系支持A和B分子之间的局域态密度决定基态的预测。
A family of organic conductors, α-(BEDT-TTF)2MHg(SCN)4, is known to show the density wave (DW) state for M = Tl, K, and Rb salts, or the superconducting (SC) state for M = NH4salt at low temperatures. In contrast, α-(BEDT-TTF)2MHg(SeCN)4shows no phase transition and retains its metallic characteristics down to low temperatures. Since no α-(BEDT-TTF)2MHg(SeCN)4salt shows the DW or SC states, it was unclear whether the system of α-(BEDT-TTF)2MHg(SeCN)4could be understood by the same phase diagram as that of α-(BEDT-TTF)2MHg(SCN)4. Here, we succeeded in synthesizing a key material, α-(BEDT-TTF)2NH4Hg(SeCN)4, and determined its crystal structure. The temperature dependence of its electric conductivity and spin susceptibility showed its DW state at low temperatures, indicating that the α-(BEDT-TTF)2MHg(SeCN)4system is linked to the α-(BEDT-TTF)2MHg(SCN)4system. From the established phase diagram, we found that the dihedral angle between crystallographically independent A and B molecules, ΘB, and that between A and C molecules, ΘC, are good tuning parameters as in θ-type BEDT-TTF salts. In the ΘB–ΘCplot, the SC salt is located in the large ΘBand small ΘCregions, whereas the metallic salts are located in the small ΘBand large ΘCregions. The DW salts are located in the intermediate ΘBand ΘCregions. The relationship between their location in the ΘB–ΘCplot and the ground states supports the prediction that the local density of state between A and B molecules determines the ground states.