Dimerization-induced spin-charge coupling in one-dimensional Mott insulators revealed by femtosecond reflection spectroscopy of Rb-tetracyanoquinodimethane salts
Dimerization-induced spin-charge coupling in one-dimensional Mott insulators revealed by femtosecond reflection spectroscopy of Rb-tetracyanoquinodimethane salts
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DOI：
10.1103/physrevb.85.125112
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发表时间：
2012-03
影响因子：
3.7
通讯作者：
H. Uemura;N. Maeshima;K. Yonemitsu;H. Okamoto
中科院分区：
文献类型：
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作者：
H. Uemura;N. Maeshima;K. Yonemitsu;H. Okamoto
利用有机化合物Rb-四氰基醌二甲烷（TCNQ）研究了晶格二聚化对一维半填充Mott绝缘体中电荷动力学的影响。首先，我们通过测量偏振拉曼光谱和光致反射率随时间的变化来研究二聚体分子位移的存在。结果表明，Rb-TCNQ在220 K以下发生了类Spin-Peierls结构相变，分子发生二聚化.其次，我们进行了飞秒反射光谱从可见光到红外区域下降到0.1 eV的Rb-TCNQ在低温阶段与二聚和高温阶段没有二聚。结果表明，分子的二聚化导致了光生载流子引起的带隙吸收的分裂。密度矩阵重整化群方法的理论计算表明，低和高能量的midgap applications是由于纯电荷激发和自旋-电荷耦合激发，分别由电子-晶格相互作用稳定的极化子。这表明，二聚破坏了具有大电子相关性的1D Mott绝缘体的自旋-电荷分离特性。
Effects of lattice dimerizations on charge dynamics in one-dimensional (1D) half-filled Mott insulators were studied using an organic compound, Rb-tetracyanoquinodimethane (TCNQ). First, we investigated the presence of the dimeric molecular displacements by the measurements of polarized Raman spectra and the time evolutions of photoinduced reflectivity changes. The results indicate that Rb-TCNQ shows a spin-Peierls-like structural phase transition and molecular dimerization occurs below 220 K. Second, we performed femtosecond reflection spectroscopy from visible to infrared regions down to 0.1 eV on Rb-TCNQ in both the low-temperature phase with dimerization and the high-temperature phase without dimerization. The results revealed that the molecular dimerization causes splitting of midgap absorption due to photocarriers. Theoretical calculations by the density-matrix renormalization group method reveal that low- and high-energy midgap absorptions are due to pure charge excitation and spin-charge-coupled excitation, respectively, of polarons stabilized by the electron-lattice interaction. This indicates that dimerization breaks the spin-charge separation characteristic of 1D Mott insulators with large electron correlation.