Ultrafast band structure control of a two-dimensional heterostructure

Søren Ulstrup, Antonija Grubišić Čabo, Jill A Miwa, Jonathon Mark Riley, Signe S Grønborg, Jens C Johannsen, Cephise Cacho, Oliver Alexander, Richard T Chapman, Emma Springate, Mario Bianchi, Maciej Dendzik, Jeppe V Lauritsen, Philip David King, Philip Hofmann

Research output: Contribution to journalArticlepeer-review

93 Citations (Scopus)
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Abstract

The electronic structure of two-dimensional (2D) semiconductors can be signicantly altered by screening effects, either from free charge carriers in the material itself, or by environmental screening from the surrounding medium. The physical properties of 2D semiconductors placed in a heterostructure with other 2D materials are therefore governed by a complex interplay of both intra- and inter-layer interactions. Here, using time- and angle-resolved photoemission, we are able to isolate both the layer-resolved band structure and, more importantly, the transient band structure evolution of a model 2D heterostructure formed of a single layer of MoS 2 on graphene. Our results reveal a pronounced renormalization of the quasiparticle gap of the MoS 2 layer. Following optical excitation, the band gap is reduced by up to ∼400 meV on femtosecond timescales due to a persistence of strong electronic interactions despite the environmental screening by the n-doped graphene. This points to a large degree of tuneability of both the electronic structure and electron dynamics for 2D semiconductors embedded in a van der Waals-bonded heterostructure.
Original languageEnglish
Pages (from-to)6315-6322
JournalACS Nano
Volume10
Issue number6
Early online date6 Jun 2016
DOIs
Publication statusPublished - 28 Jun 2016

Keywords

  • Ultrafast time- and angle-resolved photoemission
  • Band gap renormalization
  • 2D material heterostructures
  • Graphene
  • Transition metal dichalcogenides

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