Journal
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
Volume 91, Issue 2, Pages -Publisher
PHYSICAL SOC JAPAN
DOI: 10.7566/JPSJ.91.023701
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Funding
- MEXT [JP18H01166, JP20K03801, JP21H04988]
- CREST, Japan Science and Technology Agency [JPMJCR1661]
- Japan Society for the Promotion of Science (JSPS) through Program for Leading Graduate Schools (MERIT)
- JSPS Research Fellowships for Young Scientists
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In this study, the optical properties of the excitonic insulator Ta2NiSe5 were investigated using femtosecond reflection spectroscopy. The results showed that changes in excitation intensity lead to variations in the excitonic gap and a transition from an excitonic insulator to a metal. Analysis of the reflectivity also revealed a correlation between metallization and changes in the lattice structure.
An excitonic insulator, in which an optical gap is formed by exciton condensation, is expected to exhibit large photoresponses. Here, we report the results of femtosecond reflection spectroscopy covering a wide infrared region on a typical excitonic insulator, Ta2NiSe5, which gives direct information not only about a change of excitonic gap but also a metallization. With a weak excitation, the excitonic gap decreases due to the weakening of excitonic effect by photocarriers. With a strong excitation, a Drude-like high-reflection band appears, showing an excitonic-insulator-to-metal transition. Analyses of spectral and temporal changes of reflectivity revealed that the metallization is accompanied by large structural changes. This demonstrates an important role of electron-lattice interaction on the stabilization of excitonic phase.
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