Calculation of Exchange Constants in Spinels Chromites ZnxCo1-xCr2O4

The exchange interactions of the nearest-neighbor exchange constant between tetrahedral and octahedral sublattices （JAB（x））, nearest-neighbor exchange constant inside tetrahedral sublattice （JAA（x）） and nearest-neighbor exchange constant inside octahedral sublattice （JBB（x）） in cobalt and zinc chromites are calculated using the probability distribution. The Curie–Weiss temperature and the critical temperature are deduced using the mean field and the high temperature series expansion theories in ZnxCo1？xCr2O4. The critical exponent associated with the magnetic susceptibility （γ） is deduced for CoCr2O4.     

Thermal Entanglement in the Spin-S Heisenberg XYZ Model

The thermal entanglement in the spin-S Heisenberg XYZ model is studied in detail by using the entanglement measure of negativity. The effects of spin on the thermal entanglement, the threshold temperature, the critical uniform external magnetic field, the nonuniform external magnetic field and the＇, entanglement extremum are discussed, respectively. It is shown that with increasing spin, the entanglement will increase, and then decrease slowly. In addition, we find that entanglement will approach a constant Nc with the increase of DM interaction, the constant increases with the increase of spin, and both the threshold temperature Tc and critical uniform external magnetic field Bc will increase with the increasing spin. Thus high-spin system can inhibit the influence of the external environment better.     

Quark and Gluon Condensates at Finite Temperatures by the Linear Sigma Model Approach

Based on a linear sigma model, we discuss the mixing between a quark condensate and a gluon condensate. It is shown that the linear sigma model will not be self-consistent if we switch off the mixing coupling between glueball and chiral fields. By introducing a proper mixing coupling, we realize the second-order phase transitions of chiral symmetry restoration and deconfinement. We further show that the critical temperature of chirM symmetry restoration could not be larger than the temperature of deconfinement phase transition in all possible parameter spaces of our model.     

Combinative energy, oxygen deficiency and superconductivity in LnBa2Cu3O7-x （Ln=Nd, Er, Sm）

The correlation among the combinative energy, superconductivity, oxygen content, the position of holes in different planes, and the position of holes in the Cu(2)-O plane in LnBa2Cu3O7-x (Ln=Nd, Er, and Sin) has been investigated on the basis of a block model. The results indicate that the combinative energy decreases with increasing Tc in all of these compounds. And also, the combinative energies are obviously different with holes at different positions in the Cu(2)-O plane when the oxygen deficiency is low. However, this difference becomes less with increasing the oxygen deficiency.The effect of the holes in different positions on the combinative energy supplies some clue to the understanding of an unresolved problem, i.e. whether the distribution of carriers in the CuO2 plane is uniform or inhomogeneous. The results not only show that the structural characters, the combinative energy between two structural blocks and the superconductivity are closely interrelated in this class of compounds, but also reveal some differences among these systems. The relationship between the combinative energy and the Tc value in NdBa2Cu3O7-x shows some features different from the systems containing Er or Sm.     

高温超导的压力效应研究

从修正的依赖时间的金兹堡-朗道方程出发研究高温超导体的压力效应，考虑序参量为一个复数. 在外界压力作用下，理论上获得了压强与高温超导温度的一些表达式.在一些特殊情况下，得到高温超导的临界温度T随外压强的增加而降低；在另外某些条件下高温超导的临界温度T_C随外压强的增加而增加.外部施加的压强，只有一部分反映在高温超导态. 关键词： 高温超导 压强 临界温度     

超导与军事

 20世纪末是一个大动荡、大变化的时代,它的时代特点集中表现为战略格局的重新组合和高科技的迅猛发展,促进世界各国纷纷调整自己的军事战备和国家发展战略。     

通过STS对二带超导体MGB_2的π带超导相图研究(英文)

pacc:7430H Thediscoveryofthesuperconductivitywith remarkablyhighcriticaltemperature(TC～39K)inthebinaryintermetallicMgB2compound[1]hasgivenrisetoaconsiderableeffortinthecon densedmattercommunityinthelastthreeyears.Indeed,itpromisesahigheroperatingtempera …     

势场中玻色-爱因斯坦凝聚的临界温度

给出了不同于文献的势场中玻色-爱因斯坦凝聚临界温度表达式.结果揭示了势场中理想玻色子气体凝聚的临界温度与势场之间的关系，表明势场中临界温度正比于无势场情况下临界温度T０ｃ，还给出了势场的有效性判据.势场的有效性是势场与玻尔兹曼常数k和无势场情况下临界温度Ｔ０ｃ乘积ｋＴ０ｃ的比较.当势场接近或大于ｋＴ０c时，临界温度会有效增加;当势场远小于ｋＴ０c时, 势场是无效的. 关键词： 玻色-爱因斯坦凝聚 临界温度 势阱     

Three-body Force Effects on Critical Temperature of Hot Nuclear Matter

The finite temperature Brueckner-Hartree-Fock approach (FTBHF) has been extended by introducing a microscopic three-body force. The three-body force is constructed from the meson-exchange current method[1]. Within the extended FTBHF framework, the equation of state (EOS) of hot symmetric nuclear matter has been investigated and the critical temperature of the liquid-gas transition has been calculated. The obtained EOS     

EuSr2Ru1—xTaxCu2O8超导电性和磁性系的体质

通过对EuSr2Ru1-xTaxCu2O8(x=0，0．1，0．2，0．5和1．0)体系的结构、电阻和磁化强度的观测，结果发现：EuSr2RuCuO8(x=0)样品在130．2K以下呈现铁磁有序，在10K时发生了超导转变，并呈现典型的欠掺杂高温超导体特征，随着Ta对Ru替代浓度x值的增加，铁磁相变温度和超导临界温度均下降。同时，对该体系中的元素替代效应，及其磁有序和超导电性的共存进行了详细讨论。