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arXiv 2112.04485cond-mat.str-el
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电荷级Verwey跃迁时Jahn-Teller临界动力学的直接观测

Direct observation of Jahn-Teller critical dynamics at a charge-order Verwey transition

Vinícius Pascotto Gastaldo, Mala N. Rao, Alexey Bosak, Matteo d'Astuto, Andrea Prodi, Marine Verseils, Yannick Klein, Christophe Bellin, Luigi Paolasini, Adilso… 展开作者

Vinícius Pascotto Gastaldo, Mala N. Rao, Alexey Bosak, Matteo d'Astuto, Andrea Prodi, Marine Verseils, Yannick Klein, Christophe Bellin, Luigi Paolasini, Adilson J. A. de Oliveira, Edmondo Gilioli, Samrath Lal Chaplot, Andrea Gauzzi

摘要:

通过扩散和非弹性X射线散射(DS,IXS)的装置,我们探测直接的电荷有序(CO)的动力学在Verwey系统(NaMn $_3$)Mn $_4$ O $_{12}$,其中一个奇特的四重钙钛矿结构,没有氧无序稳定了几乎完整的Mn $^{3+}$ /Mn $^{4+}$静电荷顺序在$T_{\rm CO}$ =175 K伴随着相称的结构调制与传播矢量${\bf q}_{\rm CO}=(\frac{1}{2},\frac{1}{2},0)$。在$T_{\rm CO}$,IXS光谱揭示了一个35.3 meV的声子在${\bf q}_{\rm CO}$软化。晶格动力学计算使我们能够将这种软声子归因于A $_g$模式,其偏振与结构调制的Jahn-Teller样失真模式相匹配。这一结果表明,Jahn-Teller不稳定性是(NaMn $_3$)Mn $_4$ O $_{12}$中CO Verwey跃迁的驱动力,从而阐明了在磁铁矿等混合价体系中观察到的关于这种跃迁机制的长期争论。

英文摘要:

By means of diffuse and inelastic x-ray scattering (DS,IXS), we probe directly the charge-ordering (CO) dynamics in the Verwey system (NaMn$_3$)Mn$_4$O$_{12}$, where a peculiar quadruple perovskite structure with no oxygen disorder stabilizes a nearly full Mn$^{3+}$/Mn$^{4+}$ static charge order at $T_{\rm CO}$=175 K concomitant to a commensurate structural modulation with propagation vector ${\bf q}_{\rm CO}=(\frac{1}{2},\frac{1}{2},0)$. At $T_{\rm CO}$, the IXS spectra unveil a softening of a 35.3 meV phonon at ${\bf q}_{\rm CO}$. Lattice dynamical calculations enable us to attribute this soft phonon to a A$_g$ mode whose polarization matches the Jahn-Teller-like distortion pattern of the structural modulation. This result demonstrates that the Jahn-Teller instability is the driving force of the CO Verwey transition in (NaMn$_3$)Mn$_4$O$_{12}$, thus elucidating a long-standing controversy regarding the mechanism of this transition observed in other mixed-valence systems like magnetite.

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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