Monday, 16 January, 2017

Opto-valleytronic imaging of atomically thin semiconductors

Andre Neumann, Jessica Lindlau, Léo Colombier, Manuel Nutz, Sina Najmaei, Jun Lou, Aditya D. Mohite, Hisato Yamaguchi and Alexander Högele -
Nature Nanotechnology, DOI: 10.1038/NNANO.2016.282 (2017)

Transition metal dichalcogenide semiconductors represent elementary components of layered heterostructures for emergent technologies beyond conventional optoelectronics. In their monolayer form they host electrons with quantized circular motion and associated valley polarization and valley coherence as key elements of opto-valleytronic functionality. Here, we introduce two-dimensional polarimetry as means of direct imaging of the valley pseudospin degree of freedom in monolayer transition metal dichalcogenides. Using MoS₂ as a representative material with valley-selective optical transitions, we establish quantitative image analysis for polarimetric maps of extended crystals, and identify valley polarization and valley coherence as sensitive probes of crystalline disorder. Moreover, we find site-dependent thermal and non-thermal regimes of valley-polarized excitons in perpendicular magnetic fields. Finally, we demonstrate the potential of wide-field polarimetry for rapid inspection of opto-valleytronic devices based on atomically thin semiconductors and heterostructures.

Article on journal´s webpage