Light–matter interaction in van der Waals hetero-structures

Abstract

Even if individual two-dimensional materials own various interesting and unexpected properties, the stacking of such layers leads to van der Waals solids which unite the characteristics of two dimensions with novel features originating from the interlayer interactions. In this topical review, we cover fabrication and characterization of van der Waals heterosructures with a focus on heterobilayers made of monolayers of semiconducting transition metal dichalcogenides. Experimental and theoretical techniques to investigate those heterobilayers are introduced. Most recent findings focusing on different transition metal dichalcogenides heterostructures are presented and possible optical transitions between different valleys, appearance of moiré patterns and signatures of moiré excitons are discussed. The fascinating and fast growing research on van der Waals hetero-bilayers provide promising insights required for their application as emerging quantum-nano materials. arXiv:2002.08066v1 [cond-mat.mes-hall]

Two-dimensional WS2/MoS2 heterostructures: properties and applications

“…Generally, only liquid phase exfoliation is used to prepare monolayer materials rather than the further fabrication of heterostructures because the ink-printing method lacks precision and is not suitable for preparing monocrystalline TMD heterogeneous bilayers with high quality and smooth atomic interfaces. 41 On a positive side, this method has its own unique principles that deserve further study.…”

Moiré excitons in MoSe2-WSe2 heterobilayers and heterotrilayers

“…In accord with layer separation, interlayer excitons exhibit strongly prolonged radiative lifetimes 19 and reduced oscillator strength 21 . Despite numerous experimental and theoretical studies of MoSe 2 -WSe 2 HBLs, the origin of the lowestenergy PL remains a subject of debate 22 . While the majority of experimental studies interpret the HBL emission in terms of zeromomentum interlayer excitons with K or K 0 valley electrons and holes in MoSe 2 and WSe 2 15,16,19,21,[23][24][25][26][27][28][29] , others invoke excitons built from hybridized HBL conduction band states at Q pockets [30][31][32] , located roughly halfway between the center of the first Brillouin zone at Γ and K or K 0 valleys.…”

Opto-valleytronics in the 2D van der Waals heterostructure

“…As the strong correlation becomes more important and as the optovalleytronics device gets bigger, the first principle calculation based on density functional theory (DFT) or more advanced GW-BSE approximation [140,141] may not be sufficient anymore. As such, the development of approximate models that capture the important parameter dependence is critical.…”