Vikas Arora, Sukanya Pal, Luminita Harnagea, D V S Muthu, A K Sood
{"title":"激子绝缘体中相干声子模的超快动力学 \\(\\hbox {Ta}_2\\hbox {NiSe}_5\\)","authors":"Vikas Arora, Sukanya Pal, Luminita Harnagea, D V S Muthu, A K Sood","doi":"10.1007/s12043-025-02941-4","DOIUrl":null,"url":null,"abstract":"<div><p>The spontaneous condensation of excitons in the excitonic insulating phase has been reported in <span>\\(\\hbox {Ta}_2\\hbox {NiSe}_5\\)</span> (TNSe) below 325 K. In this context, we present the temperature-dependent optical pump–optical probe spectroscopy of <span>\\(\\hbox {Ta}_2\\hbox {NiSe}_5\\)</span>, 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 <span>\\(T_C=325\\)</span> 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 <span>\\(t_{\\textrm{peak}}\\)</span> of the phonons is similar for all modes except the 3 THz mode. The temperature dependence of <span>\\(t_{\\textrm{peak}}\\)</span> for the M3 mode exhibits a possible role of excitonic condensate below <span>\\(T_C\\)</span> 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.</p></div>","PeriodicalId":743,"journal":{"name":"Pramana","volume":"99 3","pages":""},"PeriodicalIF":2.1000,"publicationDate":"2025-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Ultrafast dynamics of coherent phonon modes in the excitonic insulator \\\\(\\\\hbox {Ta}_2\\\\hbox {NiSe}_5\\\\)\",\"authors\":\"Vikas Arora, Sukanya Pal, Luminita Harnagea, D V S Muthu, A K Sood\",\"doi\":\"10.1007/s12043-025-02941-4\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>The spontaneous condensation of excitons in the excitonic insulating phase has been reported in <span>\\\\(\\\\hbox {Ta}_2\\\\hbox {NiSe}_5\\\\)</span> (TNSe) below 325 K. In this context, we present the temperature-dependent optical pump–optical probe spectroscopy of <span>\\\\(\\\\hbox {Ta}_2\\\\hbox {NiSe}_5\\\\)</span>, 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 <span>\\\\(T_C=325\\\\)</span> 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 <span>\\\\(t_{\\\\textrm{peak}}\\\\)</span> of the phonons is similar for all modes except the 3 THz mode. The temperature dependence of <span>\\\\(t_{\\\\textrm{peak}}\\\\)</span> for the M3 mode exhibits a possible role of excitonic condensate below <span>\\\\(T_C\\\\)</span> 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.</p></div>\",\"PeriodicalId\":743,\"journal\":{\"name\":\"Pramana\",\"volume\":\"99 3\",\"pages\":\"\"},\"PeriodicalIF\":2.1000,\"publicationDate\":\"2025-07-08\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Pramana\",\"FirstCategoryId\":\"4\",\"ListUrlMain\":\"https://link.springer.com/article/10.1007/s12043-025-02941-4\",\"RegionNum\":4,\"RegionCategory\":\"物理与天体物理\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"PHYSICS, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Pramana","FirstCategoryId":"4","ListUrlMain":"https://link.springer.com/article/10.1007/s12043-025-02941-4","RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"PHYSICS, MULTIDISCIPLINARY","Score":null,"Total":0}
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.
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.