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EFFECTS OF ELECTRON-ELECTRON INTERACTION AND ELECTRON-PHONON COUPLING ON THE SPIN-DENSITY-WAVE OF QUASI-ONE-DIMENSIONAL ORGANIC POLYMER FERROMAGNETS 下载免费PDF全文
Based on a theoretical model proposed for quasi-one-dimensional organic polymer ferro-magnet poly-BIPO, the effects of electron-electron interaction and electron-phonon coupling on the spin-density-wave (SDW) state of poly-BIPO system are studied. It is found that the SDW state is the stable ground state of the system, in which the system shows ferromagnetic order. And the larger electron-electron interaction and the smaller electron-phonon coupling will make the SDW state more stable than the nonmagnetic state. 相似文献
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利用基于密度泛函理论平面波赝势法的第一性原理计算, 研究了过渡金属化合物OsB2和OsO2的金红石相、黄铁矿相与萤石相三种结构在高压下的状态方程和结构特性以及OsO2可能的高压相变.理论计算结果支持OsB2与OsO2的萤石相是潜在超低可压缩性的硬性材料.同时,也分析了它们的电子结构,力求理解大体变模量和高硬度的微观机制.结果表明,可以利用过渡金属高的价电子浓度,掺入硼、氧、碳、氮等轻的元素形成强的
关键词:
过渡金属化合物
密度泛函理论
低压缩性
高压 相似文献
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The Fermi surfaces (FS) of LaOFeAs (in kz = 0 plane) consist of two hole-type circles around F point, which do not touch each other, and two electron-type co-centred ellipses around the M point, which are degenerate along the M - X line. By first-principles calculations, here we show that additional degeneracy exists for the two electron-type FS, and the crucial role ofF-doping and pressure is to enhance this orbital degeneracy. It is therefore suggested that the inter-orbital fluctuation is important to understand the unconventional superconductivity in these materials. 相似文献
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Electronic structure,Dirac points and Fermi arc surface states in three-dimensional Dirac semimetal Na_3Bi from angle-resolved photoemission spectroscopy 下载免费PDF全文
梁爱基 陈朝宇 王志俊 石友国 冯娅 伊合绵 谢卓晋 何少龙 何俊峰 彭莹莹 刘艳 刘德发 胡成 赵林 刘国东 董晓莉 张君 M Nakatake H Iwasawa K Shimada M Arita H Namatame M Taniguchi 许祖彦 陈创天 翁红明 戴希 方忠 周兴江 《中国物理 B》2016,25(7):77101-077101
The three-dimensional(3D) Dirac semimetals have linearly dispersive 3D Dirac nodes where the conduction band and valence band are connected. They have isolated 3D Dirac nodes in the whole Brillouin zone and can be viewed as a 3D counterpart of graphene. Recent theoretical calculations and experimental results indicate that the 3D Dirac semimetal state can be realized in a simple stoichiometric compound A_3Bi(A = Na, K, Rb). Here we report comprehensive high-resolution angle-resolved photoemission(ARPES) measurements on the two cleaved surfaces,(001) and(100), of Na_3Bi. On the(001) surface, by comparison with theoretical calculations, we provide a proper assignment of the observed bands, and in particular, pinpoint the band that is responsible for the formation of the three-dimensional Dirac cones. We observe clear evidence of 3D Dirac cones in the three-dimensional momentum space by directly measuring on the k_x–k_y plane and by varying the photon energy to get access to different out-of-plane k_zs. In addition, we reveal new features around the Brillouin zone corners that may be related with surface reconstruction. On the(100) surface, our ARPES measurements over a large momentum space raise an issue on the selection of the basic Brillouin zone in the(100) plane. We directly observe two isolated 3D Dirac nodes on the(100) surface. We observe the signature of the Fermi-arc surface states connecting the two 3D Dirac nodes that extend to a binding energy of ~150 me V before merging into the bulk band. Our observations constitute strong evidence on the existence of the Dirac semimetal state in Na_3Bi that are consistent with previous theoretical and experimental work. In addition, our results provide new information to clarify on the nature of the band that forms the3 D Dirac cones, on the possible formation of surface reconstruction of the(001) surface, and on the issue of basic Brillouin zone selection for the(100) surface. 相似文献
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Fast impurity solver for dynamical mean field theory based on second order perturbation around the atomic limit 下载免费PDF全文
This paper proposes an impurity solver for the dynamical mean field theory (DMFT) study of the Mott insulators, which is based on the second order perturbation of the hybridization function. After careful benchmarking with quantum Monte Carlo results on the anti-ferromagnetic phase of the Hubbard model, it concludes that this impurity solver can capture the main physical features in the strong coupling regime and can be a very useful tool for the LDA (local density approximation) +,DMFT studies of the Mott insulators with long range order. 相似文献
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Band gap anomaly is a well-known issue in lead chalcogenides Pb X(X = S, Se, Te, Po). Combining ab initio calculations and tight-binding(TB) method, we have studied the band evolution in Pb X, and found that the band gap anomaly in Pb Te is mainly related to the high on-site energy of Te 5s orbital and the large s–p hopping originated from the irregular extended distribution of Te 5s electrons. Furthermore, our calculations show that Pb Po is an indirect band gap(6.5 me V) semiconductor with band inversion at L point, which clearly indicates that Pb Po is a topological crystalline insulator(TCI). The calculated mirror Chern number and surface states double confirm this conclusion. 相似文献
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