BCS-Eliashberg超导理论与二硼化镁（MgB₂）的高温超导电性

【作者】 金东泽；

【导师】 朱宰万；

【作者基本信息】 延边大学 ， 理论物理， 2004， 硕士

【摘要】 此文利用BCS弱耦合超导理论和Eliashberg强耦合超导理论研究二硼化镁（MgB₂）的高温超导电性(T_c^expt．=39K)。在弱耦合BCS理论中，该文详细报导电声子相互作用常数N（0）V计算公式和Debye温度Θ_D的计算方法，并指出，由于N（0）V推导只涉及纵向声学模与电子的相互作用，T_e=0.85Θ_D exp{（-1）／（N（0）V）)公式中的Θ_D只取纵向Debye温度即可，Θ_D→Θ_DL=（qDvl）／（kB），其结果T_c^theor．=38.7K与实验值符合极佳。 在Eliashberg强耦合理论中，此文给出有效声子谱α²（ω）F（ω）和电-声子耦合常数λ=2∫（（dω）／ω）α²（ω）F（ω）的计算公式。MgB₂超导体的理论计算表明，λ^theor．=0.749，此值较接近于国外的理论计算结果。库仑赝势μ^*theor．=0.1026，利用这些数据用McMillan T_c公式计算的T_c^McM．=26.4K。可以看出，MgB₂超导体较接近于BCS弱耦合超导材料。更多还原

【Abstract】 In this paper, We have investigated the high temperature superconductivity (T - 39/0 of MgB2 by use of the BCS weak coupling superconducting micro-scopic theory and Eliashberg strong coupling superconducting microscopic theory. In the BCS theory of weak coupling, the thesis probes into the calculating formula of the electron-phonon interaction constant N(0)V and the calculating method of Debye temperature , pointing out that since N(0)V deduction only involves the interaction between longitudinal acoustics mould and electrons, it’s passable that in the formula Tc = 0.850D exp{ only chooses the longitudinal Debye temperature, QD - QDL = sga and the result Theor- = 38.7/C perfectly tallies with the experimental values. In the theory of strong coupling, the thesis puts forward the calculating formula of the effective phonon specturum a2(u>)F(w) and the electron-phonon coupling constant A = 2(u>)F(u) . The theoretical calculation of MgB2 superconductor shows that - 0.749, the value comparatively approaches the overseas theoretical calculating result. T = 26AK is calculated by using Coulomb pseudopotential - = 1.1026, employing these data and with the formula of McMillan Tc. From this we can draw a conclusion that MgBg superconductor is comparatively near to BCS superconductive materials of weak coupling.更多还原