Evidence for impact ionization in vanadium dioxide

Joshua Holleman; Michael M. Bishop; Carlos Garcia; J. S.R. Vellore Winfred; Shinbuhm Lee; Ho Nyung Lee; Christianne Beekman; Efstratios Manousakis; Stephen A. McGill

doi:10.1103/PhysRevB.94.155129

Evidence for impact ionization in vanadium dioxide

Joshua Holleman, Michael M. Bishop, Carlos Garcia, J. S.R. Vellore Winfred, Shinbuhm Lee, Ho Nyung Lee, Christianne Beekman, Efstratios Manousakis, Stephen A. McGill

Materials Science and Technology Div

Research output: Contribution to journal › Article › peer-review

13 Scopus citations

Abstract

Pump-probe optical spectroscopy was used to investigate proposed charge-carrier multiplication via impact ionization in the M1 insulating phase of VO2. By comparing the transient reflectivities of the film when pumped at less than and then more than twice the band-gap energy, we observed a larger ultrafast response with the higher energy pump color while the film was still transiently in the insulating phase. We additionally identified multiple time scales within the charge dynamics and analyzed how these changed when the pump and probe wavelengths were varied. This experiment provided evidence that a fast carrier multiplication process, i.e., impact ionization, acts efficiently in this prototypical strongly correlated insulator, as was recently predicted by theoretical calculations.

Original language	English
Article number	155129
Journal	Physical Review B
Volume	94
Issue number	15
DOIs	https://doi.org/10.1103/PhysRevB.94.155129
State	Published - Oct 17 2016

Funding

S.M. acknowledges support from the NSF (DMR-1229217). S.L. and H.N.L. were supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. A portion of this work was performed at the National High Magnetic Field Laboratory, which was supported by National Science Foundation Cooperative Agreement No. DMR-1157490 and the State of Florida.

Funders	Funder number
State of Florida
National Science Foundation	DMR-1229217, DMR-1157490
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Division of Materials Sciences and Engineering

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title = "Evidence for impact ionization in vanadium dioxide",

abstract = "Pump-probe optical spectroscopy was used to investigate proposed charge-carrier multiplication via impact ionization in the M1 insulating phase of VO2. By comparing the transient reflectivities of the film when pumped at less than and then more than twice the band-gap energy, we observed a larger ultrafast response with the higher energy pump color while the film was still transiently in the insulating phase. We additionally identified multiple time scales within the charge dynamics and analyzed how these changed when the pump and probe wavelengths were varied. This experiment provided evidence that a fast carrier multiplication process, i.e., impact ionization, acts efficiently in this prototypical strongly correlated insulator, as was recently predicted by theoretical calculations.",

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AU - Beekman, Christianne

AU - Manousakis, Efstratios

AU - McGill, Stephen A.

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Evidence for impact ionization in vanadium dioxide

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