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Infrared Spectroscopy and Nano-Imaging of the Insulator-to-Metal Transition in Vanadium Dioxide
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- Authors
- M. M. Qazilbash, M. Brehm, G. O. Andreev, A. Frenzel, P.-C. Ho, Byung Gyu Chae, Bong Jun Kim, Sun Jin Yun, Hyun Tak Kim, A. V. Balatsky, O. G. Shpyrko, M. B. Maple, F. Keilmann, D. N. Basov
- Issue Date
- 2009-02
- Citation
- Physical Review B : Condensed Matter and Materials Physics, v.79, no.7, pp.1-10
- ISSN
- 1098-0121
- Publisher
- American Physical Society(APS)
- Language
- English
- Type
- Journal Article
- Abstract
- We present a detailed infrared study of the insulator-to-metal transition (IMT) in vanadium dioxide (VO2) thin films. Conventional infrared spectroscopy was employed to investigate the IMT in the far field. Scanning near-field infrared microscopy directly revealed the percolative IMT with increasing temperature. We confirmed that the phase transition is also percolative with cooling across the IMT. We present extensive near-field infrared images of phase coexistence in the IMT regime in VO2. We find that the coexisting insulating and metallic regions at a fixed temperature are static on the time scale of our measurements. A distinctive approach for analyzing the far-field and near-field infrared data within the Bruggeman effective medium theory was employed to extract the optical constants of the incipient metallic puddles at the onset of the IMT. We found divergent effective carrier mass in the metallic puddles that demonstrates the importance of electronic correlations to the IMT in VO2. We employ the extended dipole model for a quantitative analysis of the observed near-field infrared amplitude contrast and compare the results with those obtained with the basic dipole model. © 2009 The American Physical Society.
- KSP Keywords
- Amplitude contrast, Effective Medium Theory, Electronic correlations, Extended dipole model, Far-field and near-field, Increasing temperature, Infrared Image, Infrared Spectroscopy, Infrared data, Infrared microscopy, Infrared study