The breakdown of the adiabatic Born-Oppenheimer approximation is striking dynamical phenomenon, however, it occurs only in a handful of layered materials. Here, I show that adiabaticity breaks down in doped single-layer transition metal dichalcogenides in a quite intriguing manner. Namely, significant nonadiabatic coupling, which acts on frequencies of the Raman-active modes, is prompted by a Lifshitz transition due to depopulation and population of multiple valence and conduction valleys, respectively. The outset of the latter event is shown to be dictated by the interplay of highly non-local electron-electron interaction and spin-orbit coupling. In addition, intense electron-hole pair scatterings due to electron-phonon coupling are inducing phonon linewidth modifications as a function of doping. Comprehending these intricate dynamical effects turns out to be a key for mastering characterization of electron doping in two-dimensional nano-devices by means of Raman spectroscopy.

绝热的Born-Oppenheimer逼近的分解是惊人的动力学现象，但是，它仅在少数分层材料中发生。在这里，我表明，绝热性在掺杂的单层过渡金属二硫属化合物中以非常有趣的方式分解。即，分别由于人口减少以及多个价态和传导谷的填充而引起的Lifshitz转变促使显着的非绝热耦合作用于拉曼活性模式的频率。后者事件的开始被证明是由高度非局部电子-电子相互作用和自旋轨道耦合的相互作用决定的。另外，由于电子-声子耦合而引起的强烈的电子-空穴对散射引起声子线宽随掺杂的变化而改变。