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Imaging the nanoscale phase separation in vanadium dioxide thin films at terahertz frequencies

Stinson, H. T. and Sternbach, A. and Najera, O. and Jing, R. and Mcleod, A. S. and Slusar, T. V. and Mueller, A. and Anderegg, L. and Kim, H. T. and Rozenberg, M. and Basov, D. N. (2018) Imaging the nanoscale phase separation in vanadium dioxide thin films at terahertz frequencies. Nature Communications, 9 . Art. No. 3604. ISSN 2041-1723. PMCID PMC6127259.

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Vanadium dioxide (VO_2) 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 VO_2 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 VO_2, which account for a continuous temperature dependence of the optical response of the VO_2 in the insulating state.

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Anderegg, L.0000-0002-4282-3369
Additional Information:© 2018 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit Received 10 November 2017; Accepted 07 August 2018; Published 06 September 2018. We acknowledge the valuable discussions about optical design and principles of operation for customized terahertz instruments with Dr. Ian Gregory of TeraView Limited, Cambridge. Research at ETRI is supported by a principal project (18ZB1320). Work at UC-San Diego and Columbia University is supported by ARO-W911nf-17-1-0543. D.N.B. is the Gordon and Betty Moore Foundation’s EPiQS Initiative investigator, Grant GBMF4533. The development of THz nano-imaging is supported by ONR-DURIP: N00014-18-1-2737. The development of the cryogenic scanner and rapid sample exchange is supported by DE-SC-0012375 and DE-SC0018218. M.R. acknowledges the support by public grants from the French National Research Agency (ANR), project LACUNES No. ANR-13-BS04-0006-01, and the French–US Associated International Laboratory on Nanoelectronics funded by CNRS. Code availability: The packages used for calculating DMFT solutions are available from M.R. upon reasonable request. The packages used for calculating the lightning-rod model of the near-field signal are available from the corresponding author upon reasonable request. Data availability: The data supporting the findings of this work are available from the corresponding author upon reasonable request.
Funding AgencyGrant Number
Electronics and Telecommunications Research Institute18ZB1320
Army Research Office (ARO)W911NF-17-1-0543
Gordon and Betty Moore FoundationGBMF4533
Office of Naval Research (ONR)N00014-18-1-2737
Department of Energy (DOE)DE-SC-0012375
Department of Energy (DOE)DE-SC0018218
Agence Nationale pour la Recherche (ANR)ANR-13-BS04-0006-01
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
PubMed Central ID:PMC6127259
Record Number:CaltechAUTHORS:20180910-103057873
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89483
Deposited By: Tony Diaz
Deposited On:10 Sep 2018 18:12
Last Modified:03 Oct 2019 20:16

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