Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor

• Published in: Nature materials Vol. 13; no. 12; pp. 1091 - 1095
• Main Authors: Ugeda, Miguel M., Bradley, Aaron J., Shi, Su-Fei, da Jornada, Felipe H., Zhang, Yi, Qiu, Diana Y., Ruan, Wei, Mo, Sung-Kwan, Hussain, Zahid, Shen, Zhi-Xun, Wang, Feng, Louie, Steven G., Crommie, Michael F.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-12-2014; Nature Publishing Group
• Subjects: 136/138; 140/133; 639/301/119/1000/1018; 639/301/119/995; 639/766/119/1000/1018; Binding energy; Biomaterials; Condensed Matter Physics; Electronics; Energy; Excitation; letter; Materials Science; Monolayers; Nanotechnology; Optical and Electronic Materials; Physics; Screening; Semiconductor research; Semiconductors; Spectroscopy; Transition metals; Two dimensional
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat4061

Transition metal dichalcogenides are attracting widespread attention for their appealing optoelectronic properties. Using a combination of numerical and experimental techniques, the exciton binding energy is now determined for MoSe
2
on graphene.
Two-dimensional (2D) transition metal dichalcogenides (TMDs) are emerging as a new platform for exploring 2D semiconductor physics
1
,
2
,
3
,
4
,
5
,
6
,
7
,
8
,
9
. Reduced screening in two dimensions results in markedly enhanced electron–electron interactions, which have been predicted to generate giant bandgap renormalization and excitonic effects
10
,
11
,
12
,
13
. Here we present a rigorous experimental observation of extraordinarily large exciton binding energy in a 2D semiconducting TMD. We determine the single-particle electronic bandgap of single-layer MoSe
2
by means of scanning tunnelling spectroscopy (STS), as well as the two-particle exciton transition energy using photoluminescence (PL) spectroscopy. These yield an exciton binding energy of 0.55 eV for monolayer MoSe
2
on graphene—orders of magnitude larger than what is seen in conventional 3D semiconductors and significantly higher than what we see for MoSe
2
monolayers in more highly screening environments. This finding is corroborated by our
ab initio
GW and Bethe–Salpeter equation calculations
14
,
15
which include electron correlation effects. The renormalized bandgap and large exciton binding observed here will have a profound impact on electronic and optoelectronic device technologies based on single-layer semiconducting TMDs.