激子绝缘体中相干声子模的超快动力学 \(\hbox {Ta}_2\hbox {NiSe}_5\)

IF 2.1 4区 物理与天体物理 Q2 PHYSICS, MULTIDISCIPLINARY
Pramana Pub Date : 2025-07-08 DOI:10.1007/s12043-025-02941-4
Vikas Arora, Sukanya Pal, Luminita Harnagea, D V S Muthu, A K Sood
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引用次数: 0

摘要

在325 K以下的\(\hbox {Ta}_2\hbox {NiSe}_5\) (TNSe)中,激子在激子绝缘相中发生了自发凝聚。在这种情况下,我们提出了\(\hbox {Ta}_2\hbox {NiSe}_5\)的温度依赖光泵浦-光探针光谱,重点是相干声子(CP)动力学。除了涉及激子复合的快速弛豫过程外,我们还观察到与热声子弛豫相关的慢弛豫过程的系统行为。3太赫兹模式的不对称参数和三次非调和性表明了结构跃迁跨越\(T_C=325\) K,而2太赫兹模式的有序参数和不对称性质揭示了其与TNSe激子相的耦合。相干声子模式比相应的拉曼模式表现出更小的非调和性。连续小波变换(CWT)表明,除了3thz模式外,所有模式声子的峰值时间\(t_{\textrm{peak}}\)都是相似的。M3模式\(t_{\textrm{peak}}\)的温度依赖性表明\(T_C\)以下的激子凝聚可能在准粒子(声子)的形成中起作用。CWT分析支持由光激发载流子引起的M3模的时变不对称性。本研究说明了光激发载流子在描述相干声子的结构转变和修饰中的作用,从而证明了多体效应。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Ultrafast dynamics of coherent phonon modes in the excitonic insulator \(\hbox {Ta}_2\hbox {NiSe}_5\)

The spontaneous condensation of excitons in the excitonic insulating phase has been reported in \(\hbox {Ta}_2\hbox {NiSe}_5\) (TNSe) below 325 K. In this context, we present the temperature-dependent optical pump–optical probe spectroscopy of \(\hbox {Ta}_2\hbox {NiSe}_5\), with the focus on coherent phonon (CP) dynamics. In addition to the fast relaxation process involving excitonic recombination, we observe a systematic behaviour for the slow relaxation process associated with the relaxation of hot phonons. The asymmetry parameter and cubic anharmonicity of the 3 THz mode demonstrate the structural transition across \(T_C=325\) K, whereas the nature of the order parameter and asymmetry of 2 THz modes reveal its coupling with the excitonic phase of TNSe. Coherent phonon modes display less anharmonicity than the corresponding Raman modes. Continuous wavelet transform (CWT) reveals that the peak time \(t_{\textrm{peak}}\) of the phonons is similar for all modes except the 3 THz mode. The temperature dependence of \(t_{\textrm{peak}}\) for the M3 mode exhibits a possible role of excitonic condensate below \(T_C\) in the formation of quasiparticle (phonon). CWT analysis supports the time-dependent asymmetry of the M3 mode caused by photoexcited carriers. This study illustrates the role of photoexcited carriers in depicting a structural transition and dressing of coherent phonons, hence, demonstrating many-body effects.

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来源期刊
Pramana
Pramana 物理-物理:综合
CiteScore
3.60
自引率
7.10%
发文量
206
审稿时长
3 months
期刊介绍: Pramana - Journal of Physics is a monthly research journal in English published by the Indian Academy of Sciences in collaboration with Indian National Science Academy and Indian Physics Association. The journal publishes refereed papers covering current research in Physics, both original contributions - research papers, brief reports or rapid communications - and invited reviews. Pramana also publishes special issues devoted to advances in specific areas of Physics and proceedings of select high quality conferences.
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