Researchers have observed tightly bound negative trions in monolayer MoS₂, a type of quasi-particle composed of two electrons and a hole. These trions exhibit a large binding energy (~20 meV), making them significant even at room temperature. The study reveals that monolayer MoS₂ has strong Coulomb interactions due to reduced dielectric screening and heavy carrier band masses, leading to a much larger interaction parameter (r_s) compared to conventional 2D systems. This makes monolayer MoS₂ an ideal system for studying many-body phenomena such as carrier multiplication and Wigner crystallization. The trion binding energy was determined to be 18.0 ± 1.5 meV, consistent with theoretical predictions. The optical response of monolayer MoS₂ was analyzed using absorption and photoluminescence spectroscopy, revealing the presence of both excitons and trions at room temperature. The trion features were found to be highly doping-dependent, with their emission being largely gate-independent. The study also demonstrated the valley and spin control of trions in monolayer MoS₂, showing that trion emission is nearly 100% of the same helicity as the pump light. The results highlight the potential of monolayer MoS₂ for optoelectronic and valleytronic applications. The findings open new avenues for fundamental studies of many-body interactions and for practical applications in 2D atomic crystals.Researchers have observed tightly bound negative trions in monolayer MoS₂, a type of quasi-particle composed of two electrons and a hole. These trions exhibit a large binding energy (~20 meV), making them significant even at room temperature. The study reveals that monolayer MoS₂ has strong Coulomb interactions due to reduced dielectric screening and heavy carrier band masses, leading to a much larger interaction parameter (r_s) compared to conventional 2D systems. This makes monolayer MoS₂ an ideal system for studying many-body phenomena such as carrier multiplication and Wigner crystallization. The trion binding energy was determined to be 18.0 ± 1.5 meV, consistent with theoretical predictions. The optical response of monolayer MoS₂ was analyzed using absorption and photoluminescence spectroscopy, revealing the presence of both excitons and trions at room temperature. The trion features were found to be highly doping-dependent, with their emission being largely gate-independent. The study also demonstrated the valley and spin control of trions in monolayer MoS₂, showing that trion emission is nearly 100% of the same helicity as the pump light. The results highlight the potential of monolayer MoS₂ for optoelectronic and valleytronic applications. The findings open new avenues for fundamental studies of many-body interactions and for practical applications in 2D atomic crystals.