期刊
NATURE COMMUNICATIONS
卷 9, 期 -, 页码 -出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/s41467-018-05998-5
关键词
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资金
- French National Research Agency (ANR), project LACUNES [ANR-13-BS04-0006-01]
- French-US Associated International Laboratory on Nanoelectronics - CNRS
- [18ZB1320]
- [ARO-W911nf-17-1-0543]
- [GBMF4533]
- [ONR-DURIP: N00014-18-1-2737]
Vanadium dioxide (VO2) is a material that undergoes an insulator-metal transition upon heating above 340 K. It remains debated as to whether this electronic transition is driven by a corresponding structural transition or by strong electron-electron correlations. Here, we use apertureless scattering near-field optical microscopy to compare nanoscale images of the transition in VO2 thin films acquired at both mid-infrared and terahertz frequencies, using a home-built terahertz near-field microscope. We observe a much more gradual transition when THz frequencies are utilized as a probe, in contrast to the assumptions of a classical first-order phase transition. We discuss these results in light of dynamical mean-field theory calculations of the dimer Hubbard model recently applied to VO2, which account for a continuous temperature dependence of the optical response of the VO2 in the insulating state.
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