SrFe_(2-x)Ru_xAs_2中Ru掺杂引起的自旋密度波压制

利用第一性原理计算研究了超导母体材料SrFe2As2中用Ru原子替代Fe原子引起的自旋密度波压制.尽管Ru和Fe有相同的价电子结构,但是因为Ru的4d能带比Fe的3d能带更扩展,所以这种替代仍然能很明显的改变体系的能带、费米面等电子结构信息.通过第一性原理计算,我们发现在0 x 2的掺杂区域,材料的磁性相图可以分为3个区域:(Ⅰ)条纹状反铁磁态(0.0 x 0.6);(Ⅱ)低自旋态(0.6 x 1.0);(Ⅲ)非磁性态(1.0 x2.0).我们的理论计算结果不仅和实验结果非常完美的符合,同时能很好的解释随着Ru原子替代Fe原子,样品的自旋密度波被压制,超导开始出现.

Spin Density Wave State Suppressed by Ru Doping in SrFe2-xRuxAs2

The magnetism in SrFe2-xRuxAs2 can be suppressed by electron doping with a small substitution of Fe by Co or Ni,giving the way to superconductivity.Using the virtual-crystal approximation,the research finds the isoelectronic substitution of Fe with Ru suppresses the spin-density wave characteristic of SrFe2-xRuxAs2 by decreasing the Stoner enhancement and increasing the bandwidth due to the more extended bandwidth of Ru-4d compared with that of Fe-3d.Although Ru is isoelectronic with Fe,such substitution changes the Fermi surface and band structure greatly.From the first-principle calculation,it also finds the phase diagram of SrFe2-xRuxAs2 can be sorted as three different phases:(Ⅰ)the stripe antiferromagnetic state(0.0≤x≤0.6);(Ⅱ) the low spin state(0.6≤x≤1.0) and(Ⅲ) the nonmagnetic state(1.0≤x≤2.0).In phase II,the spin-density wave is suppressed greatly,accompanying with the emergence of superconductivity.