title: Interlayer orientation-dependent light absorption and emission in monolayer semiconductor stacks.
abstract: 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 MoS2/WS2 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.
authors.affiliation: 1] Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), 77 Cheongam-Ro, Pohang 790-784, Korea [2] Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea.
authors.forename: Hoseok
authors.initials: H
authors.lastname: Heo
authors.affiliation: 1] Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), 77 Cheongam-Ro, Pohang 790-784, Korea [2] Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea.
authors.forename: Ji Ho
authors.initials: JH
authors.lastname: Sung
authors.affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea.
authors.forename: Soonyoung
authors.initials: S
authors.lastname: Cha
authors.affiliation: Department of Chemistry and Division of Advanced Nuclear Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea.
authors.forename: Bo-Gyu
authors.initials: BG
authors.lastname: Jang
authors.affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea.
authors.forename: Joo-Youn
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), 77 Cheongam-Ro, Pohang 790-784, Korea.
authors.forename: Gangtae
authors.initials: G
authors.lastname: Jin
authors.affiliation: Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), 77 Cheongam-Ro, Pohang 790-784, Korea.
authors.forename: Donghun
authors.initials: D
authors.lastname: Lee
authors.affiliation: Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), 77 Cheongam-Ro, Pohang 790-784, Korea.
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Ahn
authors.affiliation: Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), 77 Cheongam-Ro, Pohang 790-784, Korea.
authors.forename: Myoung-Jae
authors.initials: MJ
authors.lastname: Lee
authors.affiliation: Department of Chemistry and Division of Advanced Nuclear Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea.
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Shim
authors.affiliation: School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea.
authors.forename: Hyunyong
authors.initials: H
authors.lastname: Choi
authors.affiliation: 1] Center for Artificial Low Dimensional Electronic Systems, Institute for Basic Science (IBS), 77 Cheongam-Ro, Pohang 790-784, Korea [2] Division of Advanced Materials Science, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea [3] Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang 790-784, Korea.
authors.forename: Moon-Ho
authors.initials: MH
authors.lastname: Jo