Enhanced excitonic features in an anisotropic ReS/WSe heterostructure.

Two-dimensional (2D) semiconductors have opened new horizons for future optoelectronic applications through efficient light-matter and many-body interactions at quantum level. Anisotropic 2D materials like rhenium disulphide (ReS) present a new class of materials with polarized excitonic resonances. Here, we demonstrate a WSe/ReS heterostructure which exhibits a significant photoluminescence quenching at room temperature as well as at low temperatures. This indicates an efficient charge transfer due to the electron-hole exchange interaction. The band alignment of two materials suggests that electrons optically injected into WSe are transferred to ReS. Polarization resolved luminescence measurements reveal two additional polarization-sensitive exciton peaks in ReS in addition to the two conventional exciton resonances X and X. Furthermore, for ReS we observe two charged excitons (trions) with binding energies of 18 meV and 15 meV, respectively. The bi-excitons of WSe become polarization sensitive and inherit polarizing properties from the underlying ReS layers, which act as patterned substrates for top layer. Overall, our findings provide a better understanding of optical signatures in 2D anisotropic materials.