Characterization of polarization- and power-dependent excitons and trions in bulk ReS2

We demonstrate excitons and trions in bulk ReS2 at low temperatures using polarization-resolved photoluminescence (PL) spectroscopy. At 70 K, two excitons (near 1.543 and 1.576 eV) and trions (near 1.517 and 1.570 eV) with anisotropic polarization features are observed, similar with those of a thin layer. We attribute the emergence of excitons and trions in the bulk ReS2 to its weak interlayer coupling, which is distinct from typical 2D semiconductors. Based on the assignment, we further investigate incident-laser-power dependence, providing power exponents for the quasiparticles. We expect that our basic characterization of bulk ReS2 can contribute to understand various quasiparticles and their optical applications.