Fig. 2: Strain response of excitons and identification of their valley character.
From: Strain fingerprinting of exciton valley character in 2D semiconductors
a, b False color map of PL vs. strain (log-scale) in 1L-WSe2 and 1L-WS2 devices at 10 K. Dashed lines highlight the strain-dependent excitonic peaks: neutral excitons (X0), trions (X+), charged biexcitons (XX+), dark trions and their phonon replicas (Xd+), defect excitons (D0), and excitons bound to defects (XL). Insets show the PL spectra from devices at ε = 0. c, d Extracted peak positions vs. strain of various excitons from Fig. 2a and b, respectively. The shadows denote uncertainties in the exciton peak positions. The groups of peaks corresponding to a specific strain gauge factor are color-coded. The analysis of the gauge factors allows valley fingerprinting of the corresponding excitons. Note, that a pre-strain may influence the energy positions of the observed excitons66. e Cartoons depicting valley compositions of KK (blue), KQ (red), ΓQ (purple) and defect-related (green) excitons. Green arrows indicate a strain-induced shift of the K, Q, and Γ valleys with respect to the K valley in the VB.
