English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We report on a fully self-consistent Hartree-Fock calculation of interactioneffects on the Moir\'e flat bands of twisted bilayer graphene, assuming thatvalley U(1) symmetry is respected. We use realistic band structures andinteractions and focus on the charge neutrality point, where experiments havevariously reported either insulating or semimetallic behavior. Restricting thesearch to orders for which the valley U(1) symmetry remains unbroken, we findthree types of self-consistent solutions with competitive ground state energy(i) insulators that break $C_2 {\mathcal T}$ symmetry, including valley Cherninsulators (ii) spin or valley polarized insulators and (iii) rotation $C_3$symmetry breaking semimetals whose gaplessness is protected by the topology ofthe Moir\'e flat bands. We find that the relative stability of these states canbe tuned by weak strains that break $C_3$ rotation. The nematic semimetal andalso, somewhat unexpectedly, the $C_2 {\mathcal T}$ breaking insulators, arestabilized by weak strain. These ground states may be related to thesemi-metallic and insulating behaviors seen at charge neutrality, and thesample variability of their observation. We also compare with the results ofSTM measurements near charge neutrality.

Nematic topological semimetal and insulator in magic angle bilayer graphene at charge neutrality