Abstract
When twisted bilayer graphene is strained, a periodic distortion in the electron density is triggered by electron interactions, giving rise to a novel electronic state that may help explain the observed diversity of insulating behaviors.
Highlights
The discovery of superconductivity proximate to correlated insulating behavior in a variety of graphene moireheterostructures [1,2,3,4] has triggered intensive efforts to explore the phase structure of these highly tunable twodimensional materials
We explore how the trio of realistic modifications to the Bistritzer and MacDonald (BM) model introduced above—namely, substrate effects, strain, and particle-hole symmetry breaking—stabilize phases that compete with those previously proposed for the idealized situation where these modifications are absent [20,22,51,83,91,93,96,97,98,99,100,101,102,103,104]
With the parameters used in the main text, we find a direct transition from the quantized anomalous Hall (QAH) to an incommensurate Kekulespiral” (IKS) state under increasing strain
Summary
The discovery of superconductivity proximate to correlated insulating behavior in a variety of graphene moireheterostructures [1,2,3,4] has triggered intensive efforts to explore the phase structure of these highly tunable twodimensional materials. As a case in point, even at commensurate fillings some experiments [28] report gapless states or insulators with Chern numbers distinct from those of the noninteracting bands [15,29,30] This suggests that departures from the flat band or QHFM limit are non-negligible and that the competition between itineracy and localization characteristic of Hubbard physics remains relevant to TBG. [56] For completeness, we note that translational symmetry breaking has recently been observed in closely related twisted monolayer-bilayer graphene moireheterostructures [57] and was proposed theoretically to explain insulating states observed in twisted bilayer WSe2 [58] Despite these previous works, to date there has been no systematic analysis of translational symmetry breaking in realistic TBG systems, and so the extent to which such symmetry breaking is a common phenomenon across the wide range of parameters relevant to experimental samples remains unclear. In the balance of this introduction, we provide a digest of our main results, which serves to signpost the organization of the remainder of this paper
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