Electron-phonon interaction in the normal and superconducting states of MgB2 -: art. no. 020501
Electron-phonon interaction in the normal and superconducting states of MgB2 -: art. no. 020501
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DOI：
10.1103/physrevb.64.020501
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发表时间：
2001-07-01
影响因子：
3.7
通讯作者：
Andersen, OK
中科院分区：
文献类型：
--
作者：
Kong, Y;Dolgov, OV;Andersen, OK
对于 40 K 超导体 MgB2，我们从头开始计算了整个布里渊区的电子和声子结构以及电子-声子 (e-ph) 相互作用。与等电子石墨相比，MgB2 在键合西格玛带中具有空穴，其对态密度贡献了 42%：N(0) = 0.355 态/(MgB2)(eV)（自旋）。总相互作用强度 lambda = 0.87 和 lambda (tr) = 0.60，主要由西格玛孔与波数在 590 cm(-1) 附近窄范围内的键拉伸光学声子的耦合决定。与空穴一样，这些声子是准二维的，波矢接近 GammaA，其对称性为 E。π 电子对 lambda 和 lambda (tr) 仅贡献 0.25。利用 Eliashberg 理论，我们评估了正常状态电阻率、超导体中的态密度以及 B 同位素对 T-c 和 Delta (0) 的影响，并发现与实验（如果有）非常一致。 T-c = 40 K 通过 mu* = 0.10 和 2 Delta (0)/k(B)T(c) = 3.9 再现。因此，MgB2 似乎是一种中间耦合 e-ph 配对 s 波超导体。
For the 40 K superconductor MgB2, we have calculated the electronic and phononic structures and the electron-phonon (e-ph) interaction throughout the Brillouin zone ab initio. In contrast to the isoelectronic graphite, MgB2 has holes in the bonding sigma bands, which contribute 42% to the density of states: N(0) = 0.355 states/(MgB2)(eV) (spin). The total interaction strength, lambda = 0.87 and lambda (tr) = 0.60, is dominated by the coupling of the sigma holes to the bond-stretching optical phonons with wave numbers in a narrow range around 590 cm(-1). Like the holes, these phonons are quasi-two-dimensional and have wave vectors close to GammaA, where their symmetry is E. The pi electrons contribute merely 0.25 to lambda and to lambda (tr). With Eliashberg theory we evaluate the normal-state resistivity, the density of states in the superconductor, and the B-isotope effect on T-c and Delta (0), and find excellent agreement with experiments, when available. T-c = 40 K is reproduced with mu* = 0.10 and 2 Delta (0)/k(B)T(c) = 3.9. MgB2 thus seems to be an intermediate-coupling e-ph pairing s-wave superconductor.