Marian Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, PL-30059 Kraków, Poland.
J Phys Condens Matter. 2011 Jul 6;23(26):265601. doi: 10.1088/0953-8984/23/26/265601. Epub 2011 Jun 15.
We introduce an effective model for e(g) electrons to describe quasi-two-dimensional layered La(2-x)Sr(x)NiO(4) nickelates and study it using correlated wavefunctions on 8 × 8 and 6 × 6 clusters. The effective Hamiltonian includes the kinetic energy, on-site Coulomb interactions for e(g) electrons (intraorbital U and Hund's exchange J(H)) and the coupling between e(g) electrons and Jahn-Teller distortions (static modes). The experimental ground state phases with inhomogeneous charge, spin and orbital order at the dopings x = 1/3 and 1/2 are reproduced very well by the model. Although the Jahn-Teller distortions are weak, we show that they play a crucial role and stabilize the observed cooperative charge, magnetic and orbital order in the form of a diagonal stripe phase at x = 1/3 doping and a chequerboard phase at x = 1/2 doping.
我们引入了一个有效的 e(g) 电子模型来描述准二维层状 La(2-x)Sr(x)NiO(4) 镍酸盐，并使用 8×8 和 6×6 团簇上的相关波函数对其进行了研究。有效哈密顿量包括动能、e(g) 电子的局域库仑相互作用（内轨道 U 和 Hund 交换 J(H)）以及 e(g) 电子与 Jahn-Teller 变形（静态模式）之间的耦合。实验上在掺杂 x = 1/3 和 1/2 时观察到的不均匀电荷、自旋和轨道有序的基态相被模型很好地重现。尽管 Jahn-Teller 变形很弱，但我们表明它们起着至关重要的作用，并以对角条纹相的形式稳定观察到的协同电荷、磁性和轨道有序在 x = 1/3 掺杂和 x = 1/2 掺杂时的棋盘状相。
