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Title: Tracking the insulator-to-metal phase transition in VO 2 with few-femtosecond extreme UV transient absorption spectroscopy

We present coulomb correlations can manifest in exotic properties in solids, but how these properties can be accessed and ultimately manipulated in real time is not well understood. The insulator-to-metal phase transition in vanadium dioxide (VO 2) is a canonical example of such correlations. Here, few-femtosecond extreme UV transient absorption spectroscopy (FXTAS) at the vanadium M 2,3 edge is used to track the insulator-to-metal phase transition in VO 2 . This technique allows observation of the bulk material in real time, follows the photoexcitation process in both the insulating and metallic phases, probes the subsequent relaxation in the metallic phase, and measures the phase-transition dynamics in the insulating phase. An understanding of the VO 2 absorption spectrum in the extreme UV is developed using atomic cluster model calculations, revealing V 3+/d 2 character of the vanadium center. We find that the insulator-to-metal phase transition occurs on a timescale of 26 ± 6 fs and leaves the system in a long-lived excited state of the metallic phase, driven by a change in orbital occupation. Potential interpretations based on electronic screening effects and lattice dynamics are discussed. A Mott–Hubbard-type mechanism is favored, as the observed timescales and d 2 nature of themore » vanadium metal centers are inconsistent with a Peierls driving force. In conclusion, the findings provide a combined experimental and theoretical roadmap for using time-resolved extreme UV spectroscopy to investigate nonequilibrium dynamics in strongly correlated materials.« less
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. Univ. of California, Berkeley, CA (United States). Department of Chemistry
  2. Univ. of California, Berkeley, CA (United States). Department of Chemistry and Department of Physics
  3. Vanderbilt Univ., Nashville, TN (United States). Interdisciplinary Materials Science Program
  4. Vanderbilt Univ., Nashville, TN (United States). Interdisciplinary Materials Science Program and Department of Physics and Astronomy
  5. Univ. of California, Berkeley, CA (United States). Department of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division
  6. Univ. of California, Berkeley, CA (United States). Department of Chemistry and Department of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Chemical Sciences Division
Publication Date:
Grant/Contract Number:
AC02-05CH11231; AC03-76SF00098
Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 114; Journal Issue: 36; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ultrafast dynamics; vanadium dioxide; insulator-to-metal transition; extreme UV
OSTI Identifier:
1426733