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arXiv · 2003.00514

Non-Coulomb strong electron-hole binding in $Ta_2NiSe_5$ revealed by time- and angle-resolved photoemission spectroscopy

Tangwei Tang·Hongyuan Wang·Shafeng Duan·Yuanyuan Yang·Chaozhi Huang·Yanfeng Guo·Dong Qian·Wentao Zhang
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Abstract

We reveal an ultrafast purely electronic phase transition in \TNS, which is a plausible excitonic insulator, after excited by an ultrafast infrared laser pulse. Specifically, the order parameter of the strong electron-hole binding shrinks with enhancing the pump pulse, and above a critical pump fluence, a photo-excited semimetallic state is experimentally identified with the absence of ultrafast structural transition. In addition, the bare valence and conduction bands and also the effective exciton binding energy in \TNS~are determined. These findings and detailed analysis suggest a bare nonequilibrium semimetallic phase in $Ta_2NiSe_5$ and the strong electron-hole binding cannot be exclusively driven by Coulomb interaction.

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Tangwei Tang, Hongyuan Wang, Shafeng Duan, Yuanyuan Yang, Chaozhi Huang, Yanfeng Guo, Dong Qian, Wentao Zhang. 2020-03-01. Non-Coulomb strong electron-hole binding in $Ta_2NiSe_5$ revealed by time- and angle-resolved photoemission spectroscopy. https://doi.org/10.1103/physrevb.101.235148

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