# Spin-polarized two-dimensional electron/hole gases on LiCoO$_2$ layers.

### Submission summary

 As Contributors: Santosh Kumar Radha Preprint link: scipost_202011_00010v2 Date accepted: 2021-02-19 Date submitted: 2020-12-25 16:21 Submitted by: Radha, Santosh Kumar Submitted to: SciPost Physics Academic field: Physics Specialties: Condensed Matter Physics - Theory Condensed Matter Physics - Computational Approaches: Theoretical, Computational

### Abstract

First-principles calculations show the formation of a 2D spin polarized electron (hole) gas on the Li (CoO$_2$) terminated surfaces of finite slabs down to a monolayer, in remarkable contrast with the bulk band structure, which is stabilized by Li donating its electron to the CoO$_2$ layer forming a Co-$d-t_{2g}^6$ insulator. By mapping the first-principles computational results to a minimal tight-binding models corresponding to a non-chiral 3D generalization of the quadripartite Su-Schrieffer-Heeger (SSH4) model and symmetry analysis, we show that these surface states have topological origin.

Published as SciPost Phys. 10, 057 (2021)

Dear Editor,

We have added the requested changes and replies.

Best,
Santosh

### List of changes

Page 1
1) added explecitly the statement that the surface states are not topologically protected
2) reference to Zak's and Maue-Shockley's paper
3) band structure reference

Page 2
1) removed illustration from the figure 1
2)changed interaction to hopping parameters

Page 3
1) changed interaction to hopping parameters

page 4
2) again explained the absence of topological protection of the surface states

page 5
1) added a new section referencing and detailing experemental evidence

page 6/7
1) added more details and discussion on connection to topological states.

other pages
1) changed interaction to hopping parameters

### Submission & Refereeing History

Resubmission scipost_202011_00010v2 on 25 December 2020
Submission scipost_202011_00010v1 on 11 November 2020

## Reports on this Submission

### Report

The authors have addressed my questions and now the manuscript more clearly states that the surface states found in this work are not topologically protected. I have no further comments and recommend publication in Scipost Physics.

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### Report

The authors have addressed my comments. In particular, they have clarified that the surface states they find are not topological per se; they are instead related to the topological surface state of a "parent" chiral symmetric model.
I recommend publication of the revised version of the manuscript in SciPost Physics.

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### Report

The authors have fully addressed all the points I raised during the first round of review. My recommendation is to publish this paper in SciPost Physics as is. As an aside, I want to say that I appreciate very much the fact that they have also published their code and numerical data.

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