Infrared spectroscopy of few-layer excitonic insulator candidate Ta₂NiSe₅

Ta₂NiSe₅ is proposed as an excitonic insulator, which has narrow direct bandgap and high transition temperature. In this talk, we will present our infrared spectroscopy study of few-layer Ta₂NiSe₅. In addition to the large anisotropic absorption peak at about 0.4 eV reported by many previous studies, a weak but clear excitation was newly found at lower frequency. It is possibly a signature of the electron correlation or from another electronic transition.