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

Autor: Jager MF; Department of Chemistry, University of California, Berkeley, CA 94720., Ott C; Department of Chemistry, University of California, Berkeley, CA 94720.; Department of Physics, University of California, Berkeley, CA 94720., Kraus PM; Department of Chemistry, University of California, Berkeley, CA 94720., Kaplan CJ; Department of Chemistry, University of California, Berkeley, CA 94720., Pouse W; Department of Chemistry, University of California, Berkeley, CA 94720.; Department of Physics, University of California, Berkeley, CA 94720., Marvel RE; Interdisciplinary Materials Science Program, Vanderbilt University, Nashville, TN 37235., Haglund RF; Interdisciplinary Materials Science Program, Vanderbilt University, Nashville, TN 37235.; Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235., Neumark DM; Department of Chemistry, University of California, Berkeley, CA 94720; dneumark@berkeley.edu srl@berkeley.edu.; Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720., Leone SR; Department of Chemistry, University of California, Berkeley, CA 94720; dneumark@berkeley.edu srl@berkeley.edu.; Department of Physics, University of California, Berkeley, CA 94720.; Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
Jazyk: angličtina
Zdroj: Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2017 Sep 05; Vol. 114 (36), pp. 9558-9563. Date of Electronic Publication: 2017 Aug 21.
DOI: 10.1073/pnas.1707602114
Abstrakt: 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 the vanadium metal centers are inconsistent with a Peierls driving force. The findings provide a combined experimental and theoretical roadmap for using time-resolved extreme UV spectroscopy to investigate nonequilibrium dynamics in strongly correlated materials.
Competing Interests: The authors declare no conflict of interest.
Databáze: MEDLINE
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