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arXiv 1705.08089cond-mat.mtrl-sci
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Nb2O2F3高低温相的磁性和电荷有序

Magnetism and charge ordering in high- and low-temperature phases of Nb2O2F3

V. V. Gapontsev, D. I. Khomskii, S. V. Streltsov

摘要:

综上所述,我们在本文中表明,在高温($T>$ 90 K)下,Nb $_2$ O $_2$ F $_3$的磁响应与轨道选择机制有关,当部分电子形成分子轨道,而其他电子具有局部磁矩时。在GGA计算中可以看到在$T\sim$ 90 K下发生的电荷分离,但其程度($δn \sim 0.1$电子)与基于形式离子价态的天真预期相差甚远。电荷有序的机制被认为是与一个相当大的动能增益,由于形成两个分子轨道短Nb $^{3+}$ -Nb $^{3+}$二聚体的距离依赖于电子跳跃的强烈非线性引起的。我们认为,这种电荷有序化机制,不是通过减少相互作用能,而是通过增加动能来稳定的,可能在许多其他系统中起作用,特别是由结构二聚体组成的系统。

英文摘要:

To sum up, we show in the present paper that magnetic response in Nb$_2$O$_2$F$_3$ at the high-temperatures ($T>$90 K) is related to the orbital selective regime, when part of the electrons form molecular orbitals while other electrons have local magnetic moments. The charge disproportionation, which occurs at $T\sim$90 K is seen in the GGA calculations, but its degree ($δn \sim 0.1$ electron) is far from what one would expect from naive expectations based on the formal ionic valences. The mechanism of the charge ordering is argued to be related with a sizable kinetic energy gain due to formation of two molecular orbitals in short Nb$^{3+}$-Nb$^{3+}$ dimers caused by a strong nonlinearity of the distance dependence on electron hopping. We think that this mechanism of charge ordering, stabilized not by decrease of interaction energy, but rather by the gain in kinetic energy, may be operative in many other systems, especially consisting of structural dimers.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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