Ultrafast Carrier Dynamics in Two-Dimensional Electron Gas-like K-Doped MoS₂

Electronic interactions associated with atomic adsorbates on van der Waals layered transition-metal dichalcogenides such as MoS2 can induce massive electronic reconstruction that results in the formation of a metallic phase that exhibits characteristics of a two-dimensional electron gas. The impact and mechanism of quantum confinement and reduced dimensionality on the carrier dynamics in such two-dimensional systems is at present not known, but it is of paramount importance, if they are to find application in optoelectronic devices. Here, we show by a combination of angle-resolved photoemission and advanced X-ray spectroscopies that many-body interactions in reduced dimension drastically shorten carrier lifetimes and reveal how potassium intercalation in MoS2 forces orbital rehybridization to create a two-dimensional electron gas.