Fig. 1: Twist-angle dependence of the A-exciton (X) and the high-lying exciton (HX) photoluminescence (PL) at 5 K. | Nature Communications

Fig. 1: Twist-angle dependence of the A-exciton (X) and the high-lying exciton (HX) photoluminescence (PL) at 5 K.

From: Twist-angle engineering of excitonic quantum interference and optical nonlinearities in stacked 2D semiconductors

Fig. 1

a Illustration of artificial twisted-bilayer WSe2 with a stacking angle of θ. b Origin of the A-exciton PL (red arrow) under 488 nm continuous-wave excitation (blue arrow). The gray arrow indicates nonradiative relaxation. c Origin of the upconverted HX PL (UPL) (dark blue arrow) arising through an Auger-like exciton–exciton annihilation process (black circles and arrows) under resonant pumping of the A-exciton (red arrow). d Variation of the A-exciton PL (left panel) and HX UPL (right panel) with twist angle θ. The energy of X only varies within a 24 meV range as marked by the double-headed red arrow and dashed lines, while the energy of HX varies over 235 meV as marked by the blue arrow. The intervalley exciton is marked by an asterisk.

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