<?xml version='1.0' encoding='utf-8'?> <oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd"> <dc:creator>Haddadi, Fatemeh</dc:creator> <dc:creator>Wu, QuanSheng</dc:creator> <dc:creator>J. Kruchkov, Alex</dc:creator> <dc:creator>V. Yazyev, Oleg</dc:creator> <dc:date>2020-04-29</dc:date> <dc:description>We investigate twisted double bilayer graphene (TDBG), a four-layer system composed of two AB-stacked graphene bilayers rotated with respect to each other by a small angle. Our ab-initio band structure calculations reveal a considerable energy gap at the charge point neutrality that we assign to the intrinsic symmetric polarization (ISP). We then introduce the ISP effect into the tight-binding parameterization and perform calculations on TDBG models that include lattice relaxation effects down to very small twist angles. We identify a narrow region around the magic angle θ*= 1.3° characterized by a manifold of remarkably flat bands gapped out from other states even without external electric fields. To understand the fundamental origin of the magic angle in TDBG, we construct a continuum model that points to a hidden mathematical link to the twisted bilayer graphene (TBG) model, thus indicating that the band flattening is a fundamental feature of TDBG, and is not a result of external fields.</dc:description> <dc:identifier>https://archive.materialscloud.org/record/2020.0047/v1</dc:identifier> <dc:identifier>doi:10.24435/materialscloud:2020.0047/v1</dc:identifier> <dc:identifier>mcid:2020.0047/v1</dc:identifier> <dc:identifier>oai:materialscloud.org:383</dc:identifier> <dc:language>en</dc:language> <dc:publisher>Materials Cloud</dc:publisher> <dc:rights>info:eu-repo/semantics/openAccess</dc:rights> <dc:rights>Creative Commons Attribution 4.0 International https://creativecommons.org/licenses/by/4.0/legalcode</dc:rights> <dc:subject>MARVEL/DD6</dc:subject> <dc:subject>EPFL</dc:subject> <dc:subject>SNSF</dc:subject> <dc:subject>Continuum model</dc:subject> <dc:subject>Twisted double bilayer graphene</dc:subject> <dc:subject>Tight-Binding model</dc:subject> <dc:subject>WannierTools</dc:subject> <dc:subject>Magic angle</dc:subject> <dc:subject>Flat bands</dc:subject> <dc:subject>Moiré superlattice</dc:subject> <dc:title>Moiré Flat Bands in Twisted Double Bilayer Graphene</dc:title> <dc:type>Dataset</dc:type> </oai_dc:dc>