Observation of ~100% valley-coherent excitons in monolayer MoS<sub>2</sub> through giant enhancement of valley coherence time

Garima Gupta; Kenji Watanabe; Takashi Taniguchi; Kausik Majumdar

doi:10.1038/s41377-023-01220-4

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Observation of ~100% valley-coherent excitons in monolayer MoS₂ through giant enhancement of valley coherence time

Original Articles

- Observation of ~100% valley-coherent excitons in monolayer MoS₂ through giant enhancement of valley coherence time
- Light: Science & Applications Vol. 12, Issue 8, Pages: 1644-1650(2023)
- Affiliations：
  
  1.Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore, India
  2.Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
  3.International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
- Author bio：
  
  Kausik Majumdar (kausikm@iisc.ac.in)
- Funds：
- DOI：10.1038/s41377-023-01220-4
  CLC：
- Published：31 August 2023，
  
  Published Online：13 July 2023，
  
  Received：11 February 2023，
  
  Revised：16 June 2023，
  
  Accepted：27 June 2023
- Accepted：
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Gupta, P. et al. Observation of ~100% valley-coherent excitons in monolayer MoS₂ through giant enhancement of valley coherence time. Light: Science & Applications, 12, 1644-1650 (2023).
DOI：

Gupta, P. et al. Observation of ~100% valley-coherent excitons in monolayer MoS₂ through giant enhancement of valley coherence time. Light: Science & Applications, 12, 1644-1650 (2023). DOI： 10.1038/s41377-023-01220-4.

摘要

Abstract

In monolayer transition metal dichalcogenide semiconductors

valley coherence degrades rapidly due to a combination of fast scattering and inter-valley exchange interaction. This leads to a sub-picosecond valley coherence time

making coherent manipulation of exciton a highly challenging task. Using monolayer MoS

sandwiched between top and bottom graphene

here we demonstrate fully valley-coherent excitons by observing ~100% degree of linear polarization in steady state photoluminescence. This is achieved in this unique design through a combined effect of (a) suppression in exchange interaction due to enhanced dielectric screening

(b) reduction in exciton lifetime due to a fast inter-layer transfer to graphene

and (c) operating in the motional narrowing regime. We disentangle the role of the key parameters affecting valley coherence by using a combination of calculation (solutions of Bethe-Salpeter and Maialle-Silva-Sham equations) and a careful choice of design of experiments using four different stacks with systematic variation of screening and exciton lifetime. To the best of our knowledge

this is the first report in which the excitons are found to be valley coherent in the entire lifetime in monolayer semiconductors

allowing optical readout of valley coherence possible.

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Keywords

references

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Observation of ~100% valley-coherent excitons in monolayer MoS2 through giant enhancement of valley coherence time

DOI：10.1038/s41377-023-01220-4

摘要

Abstract

关键词

Keywords

references

Observation of ~100% valley-coherent excitons in monolayer MoS₂ through giant enhancement of valley coherence time