Two-dimensional stacks of dissimilar hexagonal monolayers exhibit unusual electronic, photonic and photovoltaic responses that arise from substantial interlayer excitations. Interband excitation phenomena in individual hexagonal monolayer occur in states at band edges (valleys) in the hexagonal momentum space; therefore, low-energy interlayer excitation in the hexagonal monolayer stacks can be directed by the two-dimensional rotational degree of each monolayer crystal. However, this rotation-dependent excitation is largely unknown, due to lack in control over the relative monolayer rotations, thereby leading to momentum-mismatched interlayer excitations. Here, we report that light absorption and emission in MoS 2/WS 2 monolayer stacks can be tunable from indirect-to direct-gap transitions in both spectral and dynamic characteristics, when the constituent monolayer crystals are coherently stacked without in-plane rotation misfit. Our study suggests that the interlayer rotational attributes determine tunable interlayer excitation as a new set of basis for investigating optical phenomena in a two-dimensional hexagonal monolayer system.
Bibliographical noteFunding Information:
This work was supported by the Institute for Basic Science (IBS), Korea, under the project code of IBS-R014-G1. S.C., J.-Y.K. and H.C. were supported by the National Research Foundation of Korea (NRF) through the government of Korea (MSIP) (Grants No. NRF-2011-0013255). J.H.S. was supported by Global Frontier Program through the Global Frontier Hybrid Interface Materials (2013M3A6B1078870).
All Science Journal Classification (ASJC) codes
- Biochemistry, Genetics and Molecular Biology(all)
- Physics and Astronomy(all)