arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2310.16637cond-mat.str-elcond-mat.mtrl-sci
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阻挫分子导体 $θ$-(BEDT-TTF)$_2MM'$(SCN)$_4$ 中类玻璃转变的实验与理论联合研究

Combined experimental and theoretical studies on glasslike transitions in the frustrated molecular conductors $θ$-(BEDT-TTF)$_2MM'$(SCN)$_4$

Yohei Saito, Owen Ganter, Chao Shang, Kenichiro Hashimoto, Takahiko Sasaki, Stephen M. Winter, Jens Müller, Michael Lang

AI总结:

本文通过热膨胀测量与模型计算,揭示 $θ$-(BEDT-TTF)$_2MM'$(SCN)$_4$ 家族普遍存在两个乙烯端基构象类玻璃转变,并指出其可耦合并增强玻璃态电荷动力学。

摘要:

我们给出了阻挫准二维分子导体 $θ$-(BEDT-TTF)$_2$RbZn(SCN)$_4$ 在温度 1.5 K $\leq T \leq$ 290 K 范围内的热膨胀系数结果。在 215 K 的电荷有序/结构联合转变处观察到显著的一级相变异常。此外,还发现了两个独立类玻璃转变的明确证据,分别位于 $T_{\mathrm{g}}$ = 90–100 K 和 $T_{\mathrm{g}}^\dagger$ = 120–130 K,这与此前 T. Thomas 等人在 Phys. Rev. B 105, L041114 (2022) 中报道的 $θ$-(BEDT-TTF)$_2$CsZn(SCN)$_4$ 和 $θ$-(BEDT-TTF)$_2$CsCo(SCN)$_4$ 的结果相似;后两者均不存在电荷有序/结构转变。我们的发现表明,这些类玻璃转变是 $M$ = (Rb, Cs)、$M^\prime$ = (Co, Zn) 的 $θ$-(BEDT-TTF)$_2MM^\prime$(SCN)$_4$ 家族的共同特征,与电荷有序的存在与否无关。这些结果与我们针对多种 $θ$-(BEDT-TTF)$_2MM^\prime$(SCN)$_4$ 盐中 BEDT-TTF 分子柔性乙烯端基相关类玻璃动力学的模型计算一致,该计算预测了两种不同的构象玻璃转变。此外,跃迁积分计算显示其对端基构象具有相当程度的依赖,表明其与电子自由度存在显著耦合。我们的发现支持乙烯端基的玻璃态冻结可能驱动或增强玻璃态电荷动力学这一可能性。

英文摘要:

We present results of the coefficient of thermal expansion for the frustrated quasi-two-dimensional molecular conductor $θ$-(BEDT-TTF)$_2$RbZn(SCN)$_4$ for temperatures 1.5 K $\leq T \leq$ 290 K. A pronounced first-order phase transition anomaly is observed at the combined charge-order/structural transition at 215 K. Furthermore, clear evidence is found for two separate glasslike transitions at $T_{\mathrm{g}}$ = 90-100 K and $T_{\mathrm{g}}^\dagger$ = 120-130 K, similar to previous findings for $θ$-(BEDT-TTF)$_2$CsZn(SCN)$_4$ and $θ$-(BEDT-TTF)$_2$CsCo(SCN)$_4$, reported in T. Thomas et al., Phys. Rev. B 105, L041114 (2022), both of which lack the charge-order/structural transition. Our findings indicate that these glasslike transitions are common features for the $θ$-(BEDT-TTF)$_2MM^\prime$(SCN)$_4$ family with $M$ = (Rb, Cs) and $M^\prime$ = (Co, Zn), irrespective of the presence or absence of charge order. These results are consistent with our model calculations on the glasslike dynamics associated with the flexible ethylene endgroups of the BEDT-TTF molecules for various $θ$-(BEDT-TTF)$_2MM^\prime$(SCN)$_4$ salts, predicting two different conformational glass transitions. Moreover, calculations of the hopping integrals show a substantial degree of dependence on the endgroups' conformation, suggesting a significant coupling to the electronic degrees of freedom. Our findings support the possibility that the glassy freezing of the ethylene endgroups could drive or enhance glassy charge dynamics.

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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