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Anisotropic Zeeman Splitting in YbNi4P2
by S. Karbassi, S. Ghannadzadeh, K. Kliemt, M. Brando, C. Krellner, S. Friedemann
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Submission summary
| Authors (as registered SciPost users): | Sven Friedemann |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/1808.09756v1 (pdf) |
| Date submitted: | 2018-08-30 02:00 |
| Submitted by: | Friedemann, Sven |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approach: | Experimental |
Abstract
Only very few metallic systems can be tuned such that a continuous ferromagnetic transition occurs at zero temperature. The electronic structure is predicted to be of central importance for the existence of such a quantum critical point and the associated low-energy quantum fluctuations and low-temperature properties. Here, we study Lifshitz transitions occurring as electronic bands are shifted by magnetic field in YbNi4P2 close to a ferromagnetic quantum critical point. The angular dependence of the critical fields necessary to induce a number of Lifshitz transitions follows a simple Zeeman-shift model with anisotropic g-factor. This highlights the coherent nature of the heavy quasiparticles forming a renormalised Fermi surface. We extract information on the orientation of the Fermi surface parts giving rise to the Lifshitz transitions and we determine the anisotropy of the effective g-factor to be $\eta \approx 3.8$ in good agreement with the crystal field scheme of YbNi4P2
Current status:
Reports on this Submission
Anonymous Report 2 on 2018-10-11 (Invited Report)
- Cite as: Anonymous, Report on arXiv:1808.09756v1, delivered 2018-10-11, doi: 10.21468/SciPost.Report.608
Strengths
1. Deals with interesting Yb compound close to a ferromagnetic quantum critical point.
2. Describes an angular magnetoresistance study to extract positions of Lifshitz transitions.
3. Anisotropy of the effective g-factor has been determined
Weaknesses
1. We do not learn much more about the interesting physics of YbNi4P2.
2. Quantum oscillations in the data are not analysed.
3. Fermi surface calculations and discussion are fragmentary.
Report
Karbassi et al. have performed magnetoresistance measurements on the heavy-fermion material YbNi4P2 in two different configurations: c-axis and in-plane. This material attracts attention because it is close to a FM QCP. As function of the field a number of Lifshitz transitions have been observed (Ref.13). In this paper the authors study their angular dependence. The data are used to extract the anisotropy of the effective g-factor. This is the main result.
The data are sound and the analysis is to the point, but even with these new results we do not learn much more about YbNi4P2 and FM quantum criticality. An important feature in the data is the observation of quantum oscillations, but these will be reported elsewhere… The authors show one sheet of the probably complex Fermi surface (Fig.5) and indicate neck positions, but proof therefore is lacking. The authors made an angular dependent study of quantum oscillations, which should be explored to support (or not) their idea.
Other concerns:
1. The authors mention they have a high-quality single crystal but the RRR is only 15. Indeed quantum oscillations are visible in high fields only.
2. Lifshitz transitions B4 and B8 are tabulated, but it is not described how the magnetic field values are determined from the data.
3. The information about the band structure calculations and Fermi surface is fragmentary and insufficient. Probably a full calculation with several Fermi surface sheets has been made, since the authors write “one of the f-core Fermi surface sheets”. It is ok to present only one sheet, but then a reference should be given to the full calculation.
In summary, this work presents only an incremental advance in the understanding of YbNi4P2 and as such is not strong enough for publication in SciPost. I recommend to extend the paper by an analysis of quantum oscillations and compare the Fermi surface cross sections with the calculated Fermi surface at the supposed necking points.
Requested changes
1. See concerns above.
2. Extend the paper to come to a more complete analysis using the available information
Anonymous Report 1 on 2018-9-30 (Invited Report)
- Cite as: Anonymous, Report on arXiv:1808.09756v1, delivered 2018-09-30, doi: 10.21468/SciPost.Report.599
Strengths
1- Provides useful follow-up on a recent PRL
2- Gives interesting information about the evolution of the Fermi surface of YbNi4P2 as a function of an applied magnetic field
Weaknesses
1- The abstract and the introduction contain numerous misleading and/or confusing statements.
Report
This paper provides a follow-up to a recent PRL by a similar set of authors (Ref. [13] in the MS). Specifically, it discusses additional evidence from transport data for the occurrence and locations of the nine Lifshitz transitions that were identified in Ref. [13]. It also puts observations in context by pointing out the very unusual nature of the material under consideration.
The only weakness of the paper is a series of confusing and/or misleading statements in the contextual parts, starting with the abstract. I will list these in the order in which they occur.
1) Abstract, 1st sentence: This statement is true only for clean metallic systems. In fact, Ref. [2] discusses many examples of continuous FM zero-temperature transitions in systems that contain substantial amounts of quenched disorder.
2) Abstract, 2nd sentence: As written, this implies that the prediction in question is made in the current paper. This does not seem to be the case, so this should probably read "The electronic structure has been predicted ..."
3) p.1, 1st paragraph, 4 lines down: "... is predicted to be absent ..." has the same problem: it should read "... has been predicted ..." and contain a qualifier saying that this applies to clean systems only.
4) p.1, 2nd paragraph, 2 lines down: "... suppressing a ... transition ..." The authors clearly don't mean to say that the transition is being suppressed. This needs to be rephrased as "tuning the transition temperature to zero", or something similar.
5) p.2, 2nd paragraph, 3rd line from bottom "... the topology of the Fermi surface changes slightly ...". A `slight change of topology' is something of an oxymoron. At the very least the authors need to explain what they mean by this.
6) p.2, 3rd paragraph: "Here, we provide further evidence ..." It is not clear to the referee what the authors mean to say. Do they mean "we report on signatures in the magnetoresistance that reflect LTs"? Or, "we show that signatures in the magnetoresistance can provide evidence for LTs"? Or something else?
7) p.2, just before Eq. (1): "the magnetic field of a LT" is a strange formulation. "the critical field for a LT", or "the field at which a LT occurs" would be clearer.
A few minor linguistic problems:
8) p.1, last line: "gapping" is misspelled.
9) p.2, 2nd paragraph: In the sentence "This Kondo-lattice effect ..." there is an "a" too many.
9) p.3, 2d paragraph of Sec. 2: "home-build rotator" should be "custom-built rotator" or something similar.
Requested changes
Fix the numbered issues listed in the report above.