Evidence for an Excitonic Insulator State in Ta$_2$Pd$_3$Te$_5$
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arXiv
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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2023
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| _version_ | 1866914713697255424 |
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| author | Huang, Jierui Jiang, Bei Yao, Jingyu Yan, Dayu Lei, Xincheng Gao, Jiacheng Guo, Zhaopeng Jin, Feng Li, Yupeng Yuan, Zhenyu Chai, Congcong Sheng, Haohao Pan, Mojun Chen, Famin Liu, Junde Gao, Shunye Qu, Gexing Liu, Bo Jiang, Zhicheng Liu, Zhengtai Ma, Xiaoyan Zhou, Shiming Huang, Yaobo Yun, Chenxia Zhang, Qingming Li, Shiliang Jin, Shifeng Ding, Hong Shen, Jie Su, Dong Shi, Youguo Wang, Zhijun Qian, Tian |
| author_facet | Huang, Jierui Jiang, Bei Yao, Jingyu Yan, Dayu Lei, Xincheng Gao, Jiacheng Guo, Zhaopeng Jin, Feng Li, Yupeng Yuan, Zhenyu Chai, Congcong Sheng, Haohao Pan, Mojun Chen, Famin Liu, Junde Gao, Shunye Qu, Gexing Liu, Bo Jiang, Zhicheng Liu, Zhengtai Ma, Xiaoyan Zhou, Shiming Huang, Yaobo Yun, Chenxia Zhang, Qingming Li, Shiliang Jin, Shifeng Ding, Hong Shen, Jie Su, Dong Shi, Youguo Wang, Zhijun Qian, Tian |
| contents | The excitonic insulator (EI) is an exotic ground state of narrow-gap semiconductors and semimetals arising from spontaneous condensation of electron-hole pairs bound by attractive Coulomb interaction. Despite research on EIs dating back to half a century ago, their existence in real materials remains a subject of ongoing debate. In this study, through systematic experimental and theoretical investigations, we provide evidence for the existence of an EI ground state in a van der Waals compound Ta$_2$Pd$_3$Te$_5$. Density-functional-theory calculations suggest that it is a semimetal with a small band overlap, whereas various experiments exhibit an insulating ground state with a clear band gap. Upon incorporating electron-hole Coulomb interaction into our calculations, we obtain an EI phase where the electronic symmetry breaking opens a many-body gap. Angle-resolved photoemission spectroscopy measurements exhibit that the band gap is closed with a significant change in the dispersions as the number of thermally excited charge carriers becomes sufficiently large in both equilibrium and nonequilibrium states. Structural measurements reveal a slight breaking of crystal symmetry with exceptionally small lattice distortion in the insulating state, which cannot account for the significant gap opening. Therefore, we attribute the insulating ground state with a gap opening in Ta$_2$Pd$_3$Te$_5$ to exciton condensation, where the coupling to the symmetry-breaking electronic state induces a subtle change in the crystal structure. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2312_14455 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Evidence for an Excitonic Insulator State in Ta$_2$Pd$_3$Te$_5$ Huang, Jierui Jiang, Bei Yao, Jingyu Yan, Dayu Lei, Xincheng Gao, Jiacheng Guo, Zhaopeng Jin, Feng Li, Yupeng Yuan, Zhenyu Chai, Congcong Sheng, Haohao Pan, Mojun Chen, Famin Liu, Junde Gao, Shunye Qu, Gexing Liu, Bo Jiang, Zhicheng Liu, Zhengtai Ma, Xiaoyan Zhou, Shiming Huang, Yaobo Yun, Chenxia Zhang, Qingming Li, Shiliang Jin, Shifeng Ding, Hong Shen, Jie Su, Dong Shi, Youguo Wang, Zhijun Qian, Tian Materials Science Strongly Correlated Electrons The excitonic insulator (EI) is an exotic ground state of narrow-gap semiconductors and semimetals arising from spontaneous condensation of electron-hole pairs bound by attractive Coulomb interaction. Despite research on EIs dating back to half a century ago, their existence in real materials remains a subject of ongoing debate. In this study, through systematic experimental and theoretical investigations, we provide evidence for the existence of an EI ground state in a van der Waals compound Ta$_2$Pd$_3$Te$_5$. Density-functional-theory calculations suggest that it is a semimetal with a small band overlap, whereas various experiments exhibit an insulating ground state with a clear band gap. Upon incorporating electron-hole Coulomb interaction into our calculations, we obtain an EI phase where the electronic symmetry breaking opens a many-body gap. Angle-resolved photoemission spectroscopy measurements exhibit that the band gap is closed with a significant change in the dispersions as the number of thermally excited charge carriers becomes sufficiently large in both equilibrium and nonequilibrium states. Structural measurements reveal a slight breaking of crystal symmetry with exceptionally small lattice distortion in the insulating state, which cannot account for the significant gap opening. Therefore, we attribute the insulating ground state with a gap opening in Ta$_2$Pd$_3$Te$_5$ to exciton condensation, where the coupling to the symmetry-breaking electronic state induces a subtle change in the crystal structure. |
| title | Evidence for an Excitonic Insulator State in Ta$_2$Pd$_3$Te$_5$ |
| topic | Materials Science Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2312.14455 |