Discovery of a new type of topological Weyl fermion semimetal state in MoxW1−xTe2

The recent discovery of a Weyl semimetal in TaAs offers the first Weyl fermion observed in nature and dramatically broadens the classification of topological phases. However, in TaAs it has proven challenging to study the rich transport phenomena arising from emergent Weyl fermions. The series MoxW1−xTe2 are inversion-breaking, layered, tunable semimetals already under study as a promising platform for new electronics and recently proposed to host Type II, or strongly Lorentz-violating, Weyl fermions. Here we report the discovery of a Weyl semimetal in MoxW1−xTe2 at x=25%. We use pump-probe angle-resolved photoemission spectroscopy (pump-probe ARPES) to directly observe a topological Fermi arc above the Fermi level, demonstrating a Weyl semimetal. The excellent agreement with calculation suggests that MoxW1−xTe2 is a Type II Weyl semimetal. We also find that certain Weyl points are at the Fermi level, making MoxW1−xTe2 a promising platform for transport and optics experiments on Weyl semimetals.

I find that the authors have responded nicely to my concerns. Instead of observing the Weyl nodes that is unfortunately limited by both of the apparatus and the material, they have assigned the number and the location of Weyl points from the observed kinks in the observed energy dispersion. This has successfully been achieved due to the higher angular resolutions utilizing the low energy photons. I think that thanks to nature the photoemission signal was not sacrificed by the fatal photoionization cross section for surface and bulk states. Then I can now recommend this work to be published in Nature Communications after the following minor revisions will be made. p.5: "However, as we discuss below, we can observe We expect the Weyl points to sit above the Fermi level, where the palmier and almond pockets approach each other." => Please correct this sentence in a proper way.   We thank the editors for their consideration and we are excited that they have concluded that our work likely merits publication in Nature Communications.
Below, we address the remaining critiques of the reviewers point by point.

REPORT OF REVIEWER 1
Reviewer 1: I find that the authors have answered my previous comments in a satisfactory manner. I believe the paper may be published in Nature Communications in its present form.
Authors: We thank the reviewer for her/his useful comments and we are excited that the reviewer feels our work is ready for Nature Communications.

REPORT OF REVIEWER 3
Reviewer 3: I find that the authors have responded nicely to my concerns. Instead of observing the Weyl nodes that is unfortunately limited by both of the apparatus and the material, they have assigned the number and the location of Weyl points from the observed kinks in the observed energy dispersion. This has successfully been achieved due to the higher angular resolutions utilizing the low-energy photons. I think that thanks to nature the photoemission signal was not sacrificed by the fatal photoionization cross section for surface and bulk states.
Authors: We are happy that the reviewer is satisfied by our response and we again thank the reviewer for her/his valuable remarks. The reviewer accurately summarizes the key ideas of our manuscript as far as the Weyl points, Fermi arcs and low-energy photoemission technique are concerned.
Reviewer 3: Then, I can now recommend this work to be published in Nature Communications after the following minor revisions will be made.
Authors: We are excited that the reviewer feels our work is almost ready for publication in Nature Communications.
Reviewer 3: p.5: "However, as we discuss below, we can observe We expect the Weyl points to sit above the Fermi level, where the palmier and almond pockets approach each other." ⇒ Please correct this sentence in a proper way.
Authors: We thank the reviewer for carefully reading our text. We apologize for the error in typing. We have corrected the sentence to: "We expect the Weyl points to sit above the Fermi level, where the palmier and almond pockets approach each other." We note that there is no change to the meaning of the text. We emphasize that there is no change in our intended meaning. In fact, the labels above panels (a) and (c) indicated the correct value for k y and remain unchanged. We just made a mistake and had the panels swapped.
Reviewer 3: Fig. 4g: "A close-up of the band inversion, showing a Fermi arc which connects the Weyl points and trivial surface states from above and below which merge with the bulk bands in the vicinity of the Weyl points." ⇒ I do not clearly see where is trivial surface states in the panel g.