# Opto-valleytronic imaging of atomically thin semiconductors

## TL;DR

This paper introduces two-dimensional polarimetry for direct imaging of valley pseudospin in monolayer transition metal dichalcogenides, enabling detailed analysis of valley polarization, coherence, and disorder in atomically thin semiconductors.

## Contribution

It presents a novel polarimetric imaging technique for visualizing valley pseudospin in monolayer TMDs, with quantitative analysis and applications to device inspection.

## Key findings

- Valley polarization and coherence are sensitive to crystalline disorder.
- Site-dependent thermal and non-thermal regimes of valley excitons are identified.
- Wide-field polarimetry enables rapid inspection of opto-valleytronic devices.

## Abstract

Transition metal dichalcogenide semiconductors represent elementary components of layered heterostructures for emergent technologies beyond conventional opto-electronics. 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 MoS$_2$ 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.