论文标题
MISFIT的高sebeck系数的起源
Origin of the high Seebeck coefficient of the misfit [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$] cobaltate from site-specific valency and spin-state determinations
论文作者
论文摘要
分层的不合适率[Ca $ _2 $ COO $ _3 $] $ _ {0.62} $ [COO $ _2 $]，它成为重要的热电材料〜[a。 C. Masset等。物理。 Rev. B，62，166（2000）]在过去十年中广泛探索了其高seebeck系数背后的确切机制。其复杂的晶体和电子结构在此类研究中抑制了共识。这种情况主要是由于在其两个子系统（Rocksalt [Ca $ _2 $ COO $ _3 $]和三角形[COO $ _2 $]中的化学状态，旋转状态和现场对称性的准确鉴定上很难准确识别化学状态，旋转状态和现场对称性。通过采用谐振光发射光谱和X射线吸收光谱以及电荷转移多重模拟（在COION）中，我们在两层中成功鉴定了CO的位点对称性，价值和旋转状态。我们的场地对称性观测解释了高塞贝克系数的实验价值，并确认载体在岩石层中跳跃，这与早期的报告相反，该报告与三角形COO $ _2 $层中的跳跃层相反，负责大的Seebeck系数。
Layered misfit cobaltate [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$], which emerged as an important thermoelectric material~[A. C. Masset et al. Phys. Rev. B, 62, 166 (2000)], has been explored extensively in the last decade for the exact mechanism behind its high Seebeck coefficient. Its complex crystal and electronic structures have inhibited consensus among such investigations. This situation has arisen mainly due to difficulties in accurate identification of the chemical state, spin state, and site symmetries in its two subsystems (rocksalt [Ca$_2$CoO$_3$] and triangular [CoO$_2$]). By employing resonant photoemission spectroscopy and x-ray absorption spectroscopy along with charge transfer multiplet simulations (at the Co ions), we have successfully identified the site symmetries, valencies and spin states of the Co in both layers. Our site-symmetry observations explain the experimental value of the high Seebeck coefficient and also confirm that the carriers hop within the rocksalt layer, which is in contrast to earlier reports where hopping within triangular CoO$_2$ layer has been held responsible for the large Seebeck coefficient.
