Twisted Trilayer Graphene: A Precisely Tunable Platform for Correlated Electrons

作     者：Ziyan Zhu Stephen Carr Daniel Massatt Mitchell Luskin Efthimios Kaxiras 

作者机构：Department of Physics Harvard University Cambridge Massachusetts 02138 USA Department of Statistics The University of Chicago Chicago Illinois 60637 USA School of Mathematics University of Minnesota—Twin Cities Minneapolis Minnesota 55455 USA John A. Paulson School of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 USA 

出 版 物：《Physical Review Letters》 (物理评论快报)

年 卷 期：2020年第125卷第11期

页      面：116404-116404页

核心收录：

学科分类：07[理学] 0702[理学-物理学] 

基　　金：STC Center for Integrated Quantum Materials National Science Foundation, NSF, (1922165, 1231319, 1231319) National Science Foundation, NSF Army Research Office, ARO, (W911NF-14-0247) Army Research Office, ARO 

主　　题：Density of states Electronic structure van Hove singularity Graphene 

摘      要：We introduce twisted trilayer graphene (tTLG) with two independent twist angles as an ideal system for the precise tuning of the electronic interlayer coupling to maximize the effect of correlated behaviors. As established by experiment and theory in the related twisted bilayer graphene system, van Hove singularities (VHS) in the density of states can be used as a proxy of the tendency for correlated behaviors. To explore the evolution of VHS in the twist-angle phase space of tTLG, we present a general low-energy electronic structure model for any pair of twist angles. We show that the basis of the model has infinite dimensions even at a finite energy cutoff and that no Brillouin zone exists even in the continuum limit. Using this model, we demonstrate that the tTLG system exhibits a wide range of magic angles at which VHS merge and that the density of states has a sharp peak at the charge-neutrality point through two distinct mechanisms: the incommensurate perturbation of twisted bilayer graphene’s flatbands or the equal hybridization between two bilayer moiré superlattices.