Low-energy description of the metal-insulator transition in the rare-earth nickelates
Low-energy description of the metal-insulator transition in the rare-earth nickelates
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DOI：
10.1103/physrevb.91.075128
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发表时间：
2015-02-25
影响因子：
3.7
通讯作者：
Georges, Antoine
中科院分区：
文献类型：
--
作者：
Subedi, Alaska;Peil, Oleg E.;Georges, Antoine
我们提出了稀土镍酸盐金属-绝缘体转变的简单理论描述。该理论仅涉及每个镍位点的两个轨道，对应于低能反键 e(g) 态。在单斜绝缘态下，键长歧化分裂了 e(g) 带的流形，对应于有效现场能量的调制。我们表明，当受到局部库仑斥力 U 和洪德耦合 J 时，所产生的键歧化态对于各种相互作用参数都是顺磁绝缘体。此外，我们发现，当U - 3J 较小或为负时，对于足够大的J，会发生键歧化的自发不稳定。这个最小理论强调，较小或负的电荷转移能、较大的亨德耦合以及与键歧化的强耦合是转变的关键因素。讨论了该理论图景的实验结果。
We propose a simple theoretical description of the metal-insulator transition of rare-earth nickelates. The theory involves only two orbitals per nickel site, corresponding to the low-energy antibonding e(g) states. In the monoclinic insulating state, bond-length disproportionation splits the manifold of e(g) bands, corresponding to a modulation of the effective on-site energy. We show that, when subject to a local Coulomb repulsion U and Hund's coupling J, the resulting bond-disproportionated state is a paramagnetic insulator for a wide range of interaction parameters. Furthermore, we find that when U - 3J is small or negative, a spontaneous instability to bond disproportionation takes place for large enough J. This minimal theory emphasizes that a small or negative charge-transfer energy, a large Hund's coupling, and a strong coupling to bond disproportionation are the key factors underlying the transition. Experimental consequences of this theoretical picture are discussed.