Fig. 3. Strain response of excitonic states in WSe₂ at 100 K.

a PL spectra map of a suspended WSe₂ monolayer (device 1) at T = 100 K with individual spectra shown in (b). Free excitonic states $X^0,X^{+/-},X_d^0$ red-shift with increasing strain (the dashed lines are a guide to the eye). The state $X_d^0$ develops strong intensity maxima at energies 1.63 eV (D1) and 1.45 eV (D2). The strain-independent states close to the position of D1 that we associate with defects are marked with dashed lines. See Supplementary Fig. 1 for an offset plot of the PL spectra. c High-resolution map of the region “I" from another device (device 2). The state X⁻ disappears with increasing strain while the state $X_d^0$ arises ~ 14 meV below it. d Detailed map of the region “II" from device 1 showing a maximum near ~ 1.4 eV and an avoided-crossing pattern.