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Electronic structures of ternary iron arsenides A Fe 2 As 2 ( A = Ba, Ca, or Sr)
Feng-jie MA(马锋杰), Zhong-yi LU(卢仲毅), Tao XIANG(向涛)
Front. Phys. . 2010, 5 (2 ): 150-160.
https://doi.org/10.1007/s11467-009-0076-9
We have studied the electronic and magnetic structures of the ternary iron arsenides A Fe2 As2 (A = Ba, Ca, or Sr) using the first-principles density functional theory. The ground states of these compounds are in a collinear antiferromagnetic order, resulting from the interplay between the nearest and the next-nearest neighbor superexchange antiferromagnetic interactions bridged by As 4p orbitals. The correction from the spin–orbit interaction to the electronic band structure is given. The pressure can reduce dramatically the magnetic moment and diminish the collinear antiferromagnetic order. Based on the calculations, we propose that the low energy dynamics of these materials can be described effectively by a t −J H −J 1 −J 2 -type model [arXiv: 0806.3526v2, 2008].
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Low-energy Ce spin excitations in CeFeAsO and
CeFeAsO 0.84 F 0.16
Shi-liang LI (李世亮), Dao-xin
YAO (姚道新), Yi-ming QIU (邱义铭), Hye Jung KANG, E. W. CARLSON, Jiang-ping
HU (胡江平), Gen-fu
CHEN (陈根富), Nan-lin
WANG (王楠林), Peng-cheng DAI (戴鹏程),
Front. Phys. . 2010, 5 (2 ): 161-165.
https://doi.org/10.1007/s11467-009-0077-8
We use inelastic neutron scattering to study the low-energy spin excitations of polycrystalline samples of nonsuperconducting CeFeAsO and superconducting CeFeAsO
0.84 F
0.16 . Two sharp dispersionless modes are found at 0.85 and 1.16 meV in CeFeAsO below the Ce antiferromagnetic (AF) ordering temperature of
. On warming to above
, these two modes become one broad dispersionless mode that disappears just above the Fe ordering temperature
. For superconducting CeFeAsO
0.84 F
0.16 , where Fe static AF order is suppressed, we find a weakly dispersive mode center at 0.4 meV that may arise from short-range Ce–Ce exchange interactions. Using a Heisenberg model, we simulate powder-averaged Ce spin wave excitations. Our results show that we need both Ce spin wave and crystal electric field excitations to account for the whole spectra of low-energy spin excitations.
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Ultrafast photoelectric effects and high-sensitive photovoltages in perovskite oxides and heterojunctions
Er-jia GUO, Hui-bin Lü, Kui-juan JIN, Guo-zhen YANG
Front Phys Chin. 2010, 5 (2 ): 176-182.
https://doi.org/10.1007/s11467-010-0020-z
Perovskite oxides and heterojunctions have attracted much attention due to their multifunctional properties of electricity and optics and magnetic as well as the very good chemical and thermal stability. In this brief review, we describe the novel progress of researches in the optical characteristic, including ultrafast photoelectric effects of picosecond order in perovskite oxide single crystals, thin-films and heterojunctions, high-sensitive photovoltages, the enhanced transient lateral photovoltages in perovskite oxide thin-films and heterojunctions, and the high-sensitive ultraviolet (UV) photodetectors based on perovskite oxides. The recent advances present in this paper not only could stimulate theoretical studies on the mechanism but also would open up the possibilities in the developments of optoelectronic devices based on perovskite oxides and heterojunctions.
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K± p elastic scattering in the QCD inspired eikonalized model
Ji-huan PAN(潘继环), Li-juan ZHOU(周丽娟), Wei-xing MA(马维兴)
Front Phys Chin. 2010, 5 (2 ): 215-218.
https://doi.org/10.1007/s11467-010-0026-6
Based on our previous study of the QCD inspired eikonalized model for describing vector meson photoproduction, pp , and p ˉ p elastic scattering at high energies, we apply the mode to high energy K ± p elastic scattering. The total cross section σ tot (s ), differential cross section dσ /dt , the ratio of the real part to imaginary part of the forward scattering amplitude ρ (s ), and nuclear slope parameter function β (s ) are calculated in the model. Our results show that the theoretical prediction for σ tot (s ) is in a good agreement with the experimental data within error bars of the data. For the other theoretical predictions there are no data to test the predictive power of the model. We need the corresponding experimental data to examinate the validity of our QCD inspired eikonalized model. However, our calculations clearly show that the Odderon exchange in the process makes a significant contribution to the observable of ρ (s ) and β (s ). Therefore, we may conclude that there is a good opportunity to find the QCD Odderon in the K ± p elastic scattering at high energies.
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