Condensed Matter


On the Reproducibility of Ultra-Intense Terahertz Experiments: Comment on “Sub-Cycle Insulator-to-Metal Transition in Vanadium Dioxide by Terahertz-Field-Driven Tunneling” by Giorgianni, Vicario,.. and Hauri (Arxiv:1706.00616)

Authors: Mostafa Shalaby

The manuscript by Giorgianni et al [1], and co-authored by myself, claims and concludes on a purely electronic insulator to metal transition (IMT) in VO2 using ultra-intense THz fields without any lattice interaction. The underlying mechanism behind IMT in VO2 is a highly debatable subject with the “electron-only” IMT concept being increasingly resisted in the field especially under intense excitations. If Giorgianni/Hauri’s claim were sustained, it would be an important step towards fundamental understanding of complex systems such as the model VO2 [2-4] and may have implications on low power ultrafast switching applications. The experiment was enabled by the uniquely-intense THz source I previously developed at the SwissFEL [5, 6] and is thus not possible to reproduce elsewhere under similar excitation conditions. However, some of the measurements under the reported experimental settings showed clear phonon oscillations on the short time scale, and sample damage using the maximum reported field intensities, which may be contradicting the purely electronic/non-phonon paper claims/conclusions. These measurements were known to all PSI authors (Feb./March 2017) before the paper was drafted. However, the principal authors (Giorgianni, Vicario, and Hauri) 1 decided to exclude these measurements from the paper, disapproved the call to further repeat and verify the paper measurements, and submitted it. They then publically published the text on the arXiv without the consent of all the authors. The external co-authors (from U.C. Berkeley, USA, and Tsinghua U., China) requested the addition of the note “We (Kai Liu, Junqiao Wu and Kevin Wang) were unaware of the situation, of the hidden data, and of the PSI disagreements, and we have never been contacted or informed of any of these issues. We merely provided the samples.”† The experiment was performed at a SwissFEL laboratory, but not the experimental user laboratories. This comment should not lay responsibility on the SwissFEL facility. PSI attempted to withdraw the submission, but the arXiv is non-retractable.2

Comments: 3 Pages.

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Submission history

[v1] 2017-11-27 13:28:19

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