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Robust semi-Dirac points and unconventional topological phase transitions in doped superconducting Sr2IrO4 tunnel coupled to t2g electron systems
by Mats Horsdal, Timo Hyart
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Submission summary
| Authors (as registered SciPost users): | Mats Horsdal · Timo Hyart |
| Submission information | |
|---|---|
| Preprint Link: | http://arxiv.org/abs/1705.02987v2 (pdf) |
| Date submitted: | 2017-08-10 02:00 |
| Submitted by: | Horsdal, Mats |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approach: | Theoretical |
Abstract
Semi-Dirac fermions are known to exist at the critical points of topological phase transitions requiring fine-tuning of the parameters. We show that robust semi-Dirac points can appear in a heterostructure consisting of superconducting Sr2IrO4 and a t2g electron system (t2g-ES) without fine-tuning. They are topologically stable in the presence of the symmetries of the model, metallic t2g-ES and a single active band in Sr2IrO4. If the t2g metal is coupled to two different layers of Sr2IrO4 (effectively a multiband superconductor) in a three-layer-structure the semi-Dirac points can split into two stable Dirac points with opposite chiralities. A similar transition can be achieved if the t2g-ES supports intrinsic triplet superconductivity. By considering Sr2RuO4 as an example of a t2g-ES we predict a rich topological phase diagram as a function of various parameters.
Current status:
Reports on this Submission
Report #1 by Anonymous (Referee 1) on 2017-10-2 (Invited Report)
- Cite as: Anonymous, Report on arXiv:1705.02987v2, delivered 2017-10-02, doi: 10.21468/SciPost.Report.253
Strengths
1- Careful and extensive analysis of the topic
2- The models include enough microscopic details that they are actually relevant for experiments
Weaknesses
1- Too many different models and Hamiltonians, it's hard to keep track
Report
The authors provide an in-depth analysis of the physics of a doped Sr2IrO4 layer on top of a t2g electron gas, like Sr2RuO4. They find multiple interesting phases, including semi-Dirac points. The phase diagram becomes even richer when the t2g electron gas becomes itself superconducting.
The paper is well written and provides a lot of useful information for theorists and experimentalists studying this kind of heterostructure. I therefore recommend publication.
Requested changes
1- It might help to have a Table listing all the different models (bilayer or trilayer, simplified or microscopically accurate,...) used in the paper and the conclusion reached for each of them. The paper is quite long and contains a lot of information, so it might be worth trying to summarize the main points even more.
2- The Fermi surfaces of bulk Sr2RuO4 actually have some non-trivial dependence on the out-of-plane momentum k_z if one looks at their spin-orbital content [arXiv:1303.5444].
It might therefore be an oversimplification to take the kz=0 Fermi surface to model a few layer system. Furthermore, the only monolayers of Sr2RuO4 that were made [ 1605.05669] showed some reconstruction and therefore have Fermi surfaces that are different from the bulk ones. In particular, the gamma pocket seemed to have gone through a Lifshitz transition and to be on the other side of the van Hove singularity. It might be good to check the results for a tight-binding model specifically fitted to the few-layer physics and not the bulk one.