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Non-coplanar magnetism, topological density wave order and emergent symmetry at half-integer filling of moiré Chern bands
by Patrick H. Wilhelm, Thomas C. Lang, Mathias S. Scheurer, Andreas M. Läuchli
This Submission thread is now published as
Submission summary
| Authors (as registered SciPost users): | Thomas Lang · Andreas Läuchli · Mathias Scheurer · Patrick Wilhelm |
| Submission information | |
|---|---|
| Preprint Link: | scipost_202207_00045v2 (pdf) |
| Date accepted: | 2022-12-01 |
| Date submitted: | 2022-11-15 12:14 |
| Submitted by: | Wilhelm, Patrick |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational |
Abstract
Twisted double- and mono-bilayer graphene are graphene-based moiré materials hosting strongly correlated fermions in a gate-tunable conduction band with a topologically non-trivial character. Using unbiased exact diagonalization complemented by unrestricted Hartree-Fock calculations, we find that the strong electron-electron interactions lead to a non-coplanar magnetic state, which has the same symmetries as the tetrahedral antiferromagnet on the triangular lattice and can be thought of as a skyrmion lattice commensurate with the moiré scale, competing with a set of ferromagnetic, topological charge density waves featuring an approximate emergent O(3) symmetry, ‘rotating’ the different charge density wave states into each other. Direct comparison with exact diagonalization reveals that the ordered phases are accurately described within the unrestricted Hartree-Fock approximation. Exhibiting a finite charge gap and Chern number |C|=1, the formation of charge density wave order which is intimately connected to a skyrmion lattice phase is consistent with recent experiments on these systems.
Author comments upon resubmission
In accordance with the helpful suggestions of the referees, we updated the original manuscript as follows: 1) We added an additional remark about early studies of moiré Chern bands, both theoretical and experimental, in order to give more context on the development of the field. 2) Fig. 2 (b) was updated with a y-axis label, replacing the single entry in the legend. 3) We increased the spacings of sub-figures in Fig. 3 – 5 for better readability. 4) A note was added to Fig. 4 – 5, clarifying the role of the G=0 superscript, as well as an explicit statement of the used system size N. 5) The definition of "MRL" in Eq. 16 was added and the typo "RL"->"MRL" above Eq. 17 was corrected. 6) We restated the definitions of various variables scattered throughout the text, especially p_nu, m, Chi, phi in App. C.2.
Published as SciPost Phys. 14, 040 (2023)