Effect of intravalley and intervalley electron-hole exchange on the nonlinear optical response of monolayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>MoSe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

The coherent third-order nonlinear response of monolayer transition-metal dichalcogenide semiconductors, such as ${\mathrm{MoSe}}_{2}$, is dominated by the exciton response, well biexciton and trion resonances. fact that these resonances may be spectrally close together makes identification signatures, for example in differential transmission (DT), challenging. Instead focusing on explaining a given set experimental data, systematic study aimed at elucidating roles intravalley intervalley long-range electron-hole $(e\ensuremath{-}\mathrm{h})$ exchange DT spectra presented. Previous works have shown $e\ensuremath{-}\mathrm{h}$ introduces linear leading-order term dispersion. Based generalized Lippmann-Schwinger equation, we show presence this dispersion can reduce binding energy to zero, contrary conventional situation quadratic where an arbitrarily weak (well-behaved) attractive interaction always supports bound state(s). effects spin scattering spin-orbit caused are also clarified, line shape resonance studied function strength. In particular, determined interplay susceptibility bound-state two-exciton $T$ matrix, similarly exciton-trion matrix.