Probing uniform and nonuniform charge ordering with polarized femtosecond optical pulses in geometrically frustrated θ－(BEDT－ TTF) 2 M Zn (SCN) 4 (M= Rb, Cs)
Probing uniform and nonuniform charge ordering with polarized femtosecond optical pulses in geometrically frustrated θ－(BEDT－ TTF) 2 M Zn (SCN) 4 (M= Rb, Cs)
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几何受抑θ－(BEDT－ TTF) 2 M Zn (SCN) 4 (M= Rb, Cs) 中偏振飞秒光脉冲探测均匀和非均匀电荷有序性
DOI：
10.1103/physrevresearch.5.013024
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发表时间：
2023
影响因子：
4.2
通讯作者：
Toda Y.
中科院分区：
文献类型：
--
作者：
Nakagawa K.;Tsuchiya S.;Taniguchi H.;Toda Y.
在这项工作中，我们研究了极化分辨光致载流子弛豫动力学与几何阻挫有机导体（M= Rb，Cs）中的电荷有序（CO）作为温度的函数。在（M= Rb），偏振相关（各向异性）和独立（各向同性）的动力学表现出类似的温度依赖性。此外，瞬态反射率振幅的不连续变化和弛豫时间的增强，观察到只有在加热附近。这与长程CO引起的一级相变有关，但在（M= Cs）中，当阻挫比中强时，当温度降低到150 K以下时，各向异性分量仅略有减小，而各向同性分量逐渐增大，无滞后现象.结果表明，CO的形成是不均匀的，即出现了多个短程CO畴，并且以不同的取向分布。此外，我们发现各向异性动力学随弛豫时间的延长在低于50 K的温度下得到抑制，而各向同性动力学随弛豫时间的延长单调增长。它们之间的显着差异表明发生的结构转变，其中晶格随机变形，以匹配玻璃态电荷分布由于电荷晶格耦合。
In this work, we investigated polarization-resolved photoinduced carrier relaxation dynamics associated with charge ordering (CO) in geometrically frustrated organic conductors(M= Rb, Cs) as a function of temperature. In(M= Rb), a polarization-dependent (anisotropic) and independent (isotropic) dynamics show similar temperature dependence. Moreover, discontinuous changes in transient reflectivity amplitude and an enhancement of a relaxation time are observed only upon heating near. This is associated with the first order phase transition due to long-range CO. However, in(M= Cs) where the frustration is stronger than that in, as temperature decreases below150 K, the anisotropic component only slightly decreases while the isotropic one increases gradually without hysteresis. The behaviors indicate that CO is formed nonuniformly, that is, multiple short-range CO domains appear and are distributed with different orientations. Moreover, we found that the anisotropic dynamics with long-relaxation times suppress below50 K, which is lower than the charge glass transition temperature of100 K, whereas the isotropic dynamics grows monotonically. The distinct difference between them suggests the occurrence of a structural transition in which the lattice deforms randomly to match a glassy charge distribution due to the charge-lattice coupling.