Double Resonance Raman Scattering in Single-Layer MoSe_2 under Moderate Pressure

Pressure-dependent properties in layered transition-dichalcogenides are important for our understanding of their basic structures and applications. We investigate the electronic structure in MoSe_2 monolayer under external pressure up to 5.73 GPa by Raman spectroscopy and photoluminescence (PL) spectroscopy. The double resonance out-of-plane acoustic mode (2ZA) phonon is observed in Raman spectroscopy near 250 cm^-1, which presents pronounced intensity and pressure dependence. Significant variation in 2ZA peak intensity under different pressures reflects the change in electronic band structure as pressure varies, which is consistent with the blue shift in PL spectroscopy. The high sensitivity in both Raman and PL spectroscopy under moderate pressure in such a two-dimensional material may have many advantages for optoelectronic applications.