Angle-tunable intersubband photoabsorption and enhanced photobleaching in twisted bilayer graphene  

作　　者：Eva A.A.Pogna Xianchong Miao Driele von Dreifus Thonimar V.Alencar Marcus V.O.Moutinho Pedro Venezuela Cristian Manzoni Minbiao Ji Giulio Cerullo Ana Maria de Paula 

机构地区：[1]Istituto di Nanoscienze CNR-NANO,Laboratory NEST,Piazza San Silvestro 12,Pisa 56127,Italy [2]State Key Laboratory of Surface Physics and Department of Physics,Fudan University,Shanghai 200433,China [3]Departamento de Fisica,Institute de Ciencias Exatas,Universidade Federal de Minas Gerais,Belo Horizonte-MG 31270-901,Brazil [4]Departamento de Fisica,Institute de Ciencias Exatas e Biologicas,Universidade Federal de Ouro Preto,Ouro Preto-MG 35400-000,Brazil [5]Ndcleo Multidisciplinar de Pesquisas em Computagao-NUMPEX-COMP,Campus Duque de Caxias,Universidade Federal do Rio de Janeiro,Duque de Caxias-RJ25265-970,Brazil [6]Institute de Fisica,Universidade Federal Fluminense,UFF,Niteroi-RJ24210-346,Brazil [7]IFN-CNR,Dipartimento di Fisica,Politecnico di Milano,Piazza L.da Vinci 32,Milano 20133,Italy

出　　处：《Nano Research》2021年第8期2797-2804,共8页纳米研究（英文版）

基　　金：support from Graphene FET Flagship Core 3 Project,Grant No.881603;the Brazilian funding agencies:FAPERJ(grant number E-26/010.101126/2018),Fapemig,CNPq,Capes and INCT Carbon Nanomaterials.Prof.

摘　　要：Van der Waals heterostructures obtained by artificially stacking two-dimensional crystals represent the frontier of material engineering,demonstrating properties superior to those of the starting materials.Fine control of the interlayer twist angle has opened new possibilities for tailoring the optoelectronic properties of these heterostructures.Twisted bilayer graphene with a strong interlayer coupling is a prototype of twisted heterostructure inheriting the intriguing electronic properties of graphene.Understanding the effects of the twist angle on its out-of-equilibrium optical properties is crucial for devising optoelectronic applications.With this aim,we here combine excitation-resolved hot photoluminescence with femtosecond transient absorption microscopy.The hot charge carrier distribution induced by photo-excitation results in peaked absorption bleaching and photo-induced absorption bands,both with pronounced twist angle dependence.Theoretical simulations of the electronic band structure and of the joint density of states enable to assign these bands to the blocking of interband transitions at the van Hove singularities and to photo-activated intersubband transitions.The tens of picoseconds relaxation dynamics of the observed bands is attributed to the angle-dependence of electron and phonon heat capacities of twisted bilayer graphene.

关 键 词：twisted bilayer graphene transient absorption microscopy hot-photoluminescence van der Waals heterostructures optoelectronic properties van Hove singularities 

分 类 号：TQ127.11[化学工程—无机化工]