Journal
NATURE PHYSICS
Volume 17, Issue 9, Pages 1024-+Publisher
NATURE PORTFOLIO
DOI: 10.1038/s41567-021-01289-x
Keywords
-
Categories
Funding
- Institute for Basic Science (IBS), Korea [IBS-R014-D01]
- National Research Foundation of Korea (NRF) through the SRC [2018R1A5A6075964]
- Max Planck-POSTECH Center [2016K1A4A4A01922028]
Ask authors/readers for more resources
Low-temperature ARPES measurements on Ta2NiSe5 provide evidence for the spontaneous formation of excitons, shedding light on their important roles in optoelectronics, photovoltaics, and photosynthesis. The study also reveals the potential for excitons to form spontaneously in small-gap semiconductors or semimetals, leading to Bose-Einstein condensation at low temperatures. This detection of spontaneously formed excitons in a debated excitonic insulator candidate, Ta2NiSe5, guarantees the excitonic insulator nature of the material at low temperature.
Excitons have been predicted to form spontaneously-without external excitation-in some materials. Low-temperature ARPES measurements on Ta2NiSe5 now provide evidence for such an excitonic insulator and for so-called preformed excitons. Excitons, quasiparticles of electrons and holes bound by Coulombic attraction, are created transiently by light and play an important role in optoelectronics, photovoltaics and photosynthesis. They are also predicted to form spontaneously in a small-gap semiconductor or a semimetal, leading to a Bose-Einstein condensate at low temperature, but there has not been any direct evidence of this effect so far. Here we detect the photoemission signal from spontaneously formed excitons in a debated excitonic insulator candidate, Ta2NiSe5. Our symmetry-selective angle-resolved photoemission spectroscopy reveals a characteristic excitonic feature above the transition temperature, which provides detailed properties of excitons, such as the anisotropic Bohr radius. The present result provides evidence for so-called preformed excitons and guarantees the excitonic insulator nature of Ta2NiSe5 at low temperature.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available