Journal article
Nematicity with a twist: Rotational symmetry breaking in a moire superlattice
SCIENCE ADVANCES, v 6(32), eaba8834
Aug 2020
PMID: 32821828
Abstract
Motivated by recent reports of nematic order in twisted bilayer graphene (TBG), we investigate the impact of the triangular moire superlattice degrees of freedom on nematicity. In TBG, the nematic order parameter is not Ising like, as in tetragonal crystals, but has a three-state Potts character related to the threefold rotational symmetry (C-3z) of the moire superlattice. We find that, even in the presence of static strain that explicitly breaks the C-3z symmetry, the system can still undergo a nematic-flop phase transition that spontaneously breaks in-plane twofold rotations. Moreover, elastic fluctuations, manifested as acoustic phonons, mediate a nemato-orbital coupling that ties the nematic director orientation to certain soft directions in momentum space, rendering the Pottsnematic transition mean field and first order. In contrast to the case of rigid crystals, the Fermi surface hot spots associated with these soft directions are maximally coupled to low-energy nematic fluctuations in the moire superlattice case.
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Details
- Title
- Nematicity with a twist: Rotational symmetry breaking in a moire superlattice
- Publication Details
- SCIENCE ADVANCES, v 6(32), eaba8834
- Publisher
- AMER ASSOC ADVANCEMENT SCIENCE; WASHINGTON
- Grant note
- R.M.F. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under award no. DE-SC0020045.
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- Drexel University
- Web of Science ID
- WOS:000560452300016
- Scopus ID
- 2-s2.0-85089802533
- Other Identifier
- 991021860671704721
InCites Highlights
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- Collaboration types
- Domestic collaboration
- Web of Science research areas
- Physics, Condensed Matter