Multivalley systems offer not only exciting physical phenomena but also the possibility of broad utilization. Identifying an important platform and understanding its physics are paramount tasks to improve their capability for application. Here, we investigate a promising candidate, the semiconductor SnSe, by optical spectroscopy and density functional theory calculations. Upon applying pressure to lightly doped SnSe, we directly monitored the phase transition from semiconductor to semimetal. In addition, heavily doped SnSe exhibited a successive Lifshitz transition, activating multivalley physics. Our comprehensive study provides insight into the effects of pressure and doping on this system, leading to promising routes to tune the material properties for advanced device applications, including thermoelectrics and valleytronics.

多谷系统不仅提供令人兴奋的物理现象，而且还提供了广泛利用的可能性。识别重要平台并了解其物理原理是提高其应用能力的首要任务。在这里，我们通过光谱学和密度泛函理论计算研究了有前途的候选半导体SnSe。在对轻掺杂SnSe施加压力后，我们直接监测了从半导体到半金属的相变。此外，重掺杂SnSe表现出连续的Lifshitz跃迁，从而激活了多谷物理学。我们的综合研究深入了解了压力和掺杂对该系统的影响，从而为优化包括热电和Valleytronics在内的高级设备应用的材料性能提供了有希望的途径。