Role of entropy and structural parameters in the spin-state transition of LaCoO3
Role of entropy and structural parameters in the spin-state transition of LaCoO3
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DOI：
10.1103/physrevmaterials.1.064403
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发表时间：
2017-11-08
影响因子：
3.4
通讯作者：
Haule, Kristjan
中科院分区：
文献类型：
--
作者：
Chakrabarti, Bismayan;Birol, Turan;Haule, Kristjan
尽管理论和实验都付出了努力，但 LaCoO3 中的自旋态转变几十年来一直未能得到描述。在本研究中，我们使用完全电荷自洽密度泛函理论+嵌入式动态平均场理论（DFT+DMFT）来解决这个问题。我们从第一原理证明 LaCoO3 在任何温度下都不能用单一的纯自旋态来描述。相反，我们观察到随着温度的升高，高自旋多重态的数量逐渐变化，高自旋多重态在自旋态转变开始时被激发，随后中间自旋多重态在金属-绝缘体转变温度下被激发。我们明确阐明了晶格膨胀和氧八面体旋转在自旋态转变中的关键作用。我们还根据第一原理重现了 LaCoO3 中的自旋态转变和金属-绝缘体转变发生在不同的温度尺度。此外，我们的结果揭示了电子熵在驱动自旋态转变中的重要性，迄今为止，这一点在该材料的所有第一性原理研究中都被忽略了。
The spin-state transition in LaCoO3 has eluded description for decades despite concerted theoretical and experimental effort. In this study, we approach this problem using fully charge self-consistent density functional theory + embedded dynamical mean field theory (DFT+DMFT). We show from first principles that LaCoO3 cannot be described by a single, pure spin state at any temperature. Instead, we observe a gradual change in the population of higher-spin multiplets with increasing temperature, with the high-spin multiplets being excited at the onset of the spin-state transition followed by the intermediate-spin multiplets being excited at the metal-insulator-transition temperature. We explicitly elucidate the critical role of lattice expansion and oxygen octahedral rotations in the spin-state transition. We also reproduce, from first principles, that the spin-state transition and the metal-insulator transition in LaCoO3 occur at different temperature scales. In addition, our results shed light on the importance of electronic entropy in driving the spin-state transition, which has so far been ignored in all first-principles studies of this material.