Electronic phase diagram of Cr-doped VO2 epitaxial films studied by in situ photoemission spectroscopy
| Autor: | Shiga, D., Cheng, X., Kim, T. T., Kanda, T., Hasegawa, N., Kitamura, M., Yoshimatsu, K., Kumigashira, H. |
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| Rok vydání: | 2022 |
| Předmět: | |
| Zdroj: | Phys. Rev. B 108, 045112 (2023) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevB.108.045112 |
| Popis: | Through in situ photoemission spectroscopy (PES), we investigated the changes in the electronic structure of Cr-doped VO2 films coherently grown on TiO2 (001) substrates. The electronic phase diagram of CrxV1-xO2 is drawn by a combination of electric and spectroscopic measurements. The phase diagram is similar to that of bulk CrxV1-xO2, while the temperature of metal-insulator transition (TMIT) is significantly suppressed by the epitaxial strain effect. In the range of x = 0-0.04, where TMIT remains unchanged as a function of x, the PES spectra show dramatic change across TMIT, demonstrating the characteristic spectral changes associated with the Peierls phenomenon. In contrast, for x > 0.04, the TMIT linearly increases, and the metal-insulator transition (MIT) may disappear at x = 0.08-0.12. The PES spectra at x = 0.08 exhibit pseudogap behavior near the Fermi level, whereas the characteristic temperature-induced change remains almost intact, suggesting the existence of local V-V dimerization. The suppression of V-V dimerization with increasing x was confirmed by polarization-dependent x-ray absorption spectroscopy. These spectroscopic investigations reveal that the energy gap and V 3d states are essentially unchanged with 0 $\le$ x $\le$ 0.08 despite the suppression of V-V dimerization. The invariance of the energy gap with respect to x suggests that the MIT in CrxV1-xO2 arises primarily from the strong electron correlations, namely the Peierls-assisted Mott transition. Meanwhile, the pseudogap at x = 0.08 eventually evolves to a full gap (Mott gap) at x = 0.12, which is consistent with the disappearance of the temperature-dependent MIT in the electronic phase diagram. These results demonstrate that a Mott insulating phase without V-V dimerization is stabilized at x > 0.08 as a result of the superiority of Mott instability over the Peierls one. Comment: 27 pages, 3 main figures, 5 supplementary figures. arXiv admin note: text overlap with arXiv:2005.00304 |
| Databáze: | arXiv |
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