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Visualizing near-coexistence of massless Dirac electrons and ultra-massive saddle point electrons
by Abhay Kumar Nayak, Jonathan Reiner, Hengxin Tan, Huixia Fu, Henry Ling, Chandra Shekhar, Claudia Felser, Tami Pereg-Barnea, Binghai Yan, Haim Beidenkopf, Nurit Avraham
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Submission summary
| Authors (as registered SciPost users): | Nurit Avraham |
| Submission information | |
|---|---|
| Preprint Link: | scipost_202305_00044v1 (pdf) |
| Date submitted: | May 29, 2023, 5:30 p.m. |
| Submitted by: | Avraham, Nurit |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approach: | Experimental |
Abstract
Strong singularities in the electronic density of states amplify correlation effects and play a key role in determining the ordering instabilities in various materials. Recently high or- der van Hove singularities (VHSs) with diverging power-law scaling have been classified in single-band electron models. We show that the 110 surface of Bismuth exhibits high order VHS with unusually high exponent of −0.7. Detailed mapping of the surface band structure using scanning tunneling microscopy and spectroscopy shows that this singularity occurs in close proximity with Dirac bands located at the center of the surface Brillouin zone. The enhanced power-law divergence is shown to originate from the anisotropic flattening of the Dirac band just above the Dirac node. Such near-coexistence of massless Dirac electrons and ultra-massive saddle points enables to study the interplay of high order VHS and Dirac fermions.
Current status:
Reports on this Submission
Report #2 by Anonymous (Referee 2) on 2023-7-9 (Invited Report)
- Cite as: Anonymous, Report on arXiv:scipost_202305_00044v1, delivered 2023-07-09, doi: 10.21468/SciPost.Report.7484
Strengths
- Clear focusing on a topic.
- Good presentation of experimental results with identification of main features presented in the spectrum.
- Comparison with DFT calculations for the purpose of identifying main observed features in QPI.
Weaknesses
- Number of typos (High-order van Hove singularity section, line 5 – typo “magic angel”, also in References)
- Conclusions about the origin of van Hove singularities are not fully clear.
Report
Requested changes
- What is the assumed energy as a function of momentum dependence of high-order van Hove singularity observed and shown in Fig.3. I would suggest Authors to expand discussion of symmetry properties of material that create and protect this van Hove singularity.
- On page 18 the link to Overleaf appears. I would suggest Authors to use standardized ways to publish experimental data and codes for analysis such as Zenodo repositories.
- The DoS plots presented in Fig.1 and 3 contain a clear peaks related to the main (high-order) van Hove singularity and additional small peak structure that might be related to usual van Hove singularities. In the dispersion shown in Fig.3f, e, g Authors identify positions of van Hove singularities and the approximate shape of constant energy contours thus concluding about high-order type of saddle points. From these results it might be possible to identify which saddle points exactly produce high-order van Hove singularities and why divergence exponents are different on different sides of the peak in DoS. I would suggest Authors to extend the discussion of these features, as it seems that it is already partially present in the data shown.
- What is the energy resolutions in DoS (dI/dV plot) presented in Fig.3
- I would suggest Authors to correct typos in the text and in the references list (such as in Refs.15, 16, 34 etc).
Report #1 by Anonymous (Referee 1) on 2023-7-3 (Invited Report)
- Cite as: Anonymous, Report on arXiv:scipost_202305_00044v1, delivered 2023-07-03, doi: 10.21468/SciPost.Report.7440
Strengths
(2) Good motivation for choosing the Bi(110) surface over the (111): The 110 has the surface and bulk bands well separated in energy allowing one to directly probe the former using QPI.
(3) The QPI are directly compared with Green’s function calculations based on ab initio calculations of the Bi(110) surface states to identify microscopic processes contribution to the observed signals.
Weaknesses
Report
Overall, the paper is well written with the results presented in a logical and clear fashion. The results are interesting, and the analysis is thorough. I recommend publication in SciPost.
Requested changes
(1) In the abstract, I suggest being clear about which quantity is diverging and exactly how the exponent is defined, for example $DOS(\omega) \propto \omega^{-0.7}$.
(2) In the abstract I would mention the role that theory played in reaching the conclusions about the band structure. For example, I would modify the existing sentence to the following: “Detailed mapping of the surface band structure using scanning tunneling microscopy and spectroscopy combined with first-principles calculations shows that this singularity occurs in close proximity to Dirac bands located at the center of the surface Brillouin zone. “
(3) For the opening sentence of the introduction I suggest “..ascertaining..” $\to$ “…determining..” since the DOS has a causal effect on the interacting aspects of the physics.
(4) Next line, “..upsurge..” $\to$ ”…an upsurge..”. Following line, “..logarithmic…” $\to$ “.. a logarithmic..”, etc. Please check use of articles throughout manuscript.
(5) In the section on “High-order van Hove singularity”, do the authors mean to quote a value of -0.25 (rather than 0.25) for magic angle graphene? (Also, angle is misspelled “angel” there.)