Highly anisotropic and robust excitons in monolayer black phosphorus.
Semi-metallic graphene and semiconducting monolayer transition-metal dichalcogenides are the most intensively studied two-dimensional materials of recent years. Lately, black phosphorus has emerged as a promising new two-dimensional material due to its widely tunable and direct bandgap, high carrier mobility and remarkable in-plane anisotropic electrical, optical and phonon properties. However, current progress is primarily limited to its thin-film form. Here, we reveal highly anisotropic and strongly bound excitons in monolayer black phosphorus using polarization-resolved photoluminescence measurements at room temperature. We show that, regardless of the excitation laser polarization, the emitted light from the monolayer is linearly polarized along the light effective mass direction and centres around 1.3 eV, a clear signature of emission from highly anisotropic bright excitons. Moreover, photoluminescence excitation spectroscopy suggests a quasiparticle bandgap of 2.2 eV, from which we estimate an exciton binding energy of ∼0.9 eV, consistent with theoretical results based on first principles. The experimental observation of highly anisotropic, bright excitons with large binding energy not only opens avenues for the future explorations of many-electron physics in this unusual two-dimensional material, but also suggests its promising future in optoelectronic devices.
Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, USA.
Xiaomu
X
Wang
Department of Physics and Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA.
Aaron M
0000000283261294
AM
Jones
Department of Physics and Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA.
Kyle L
KL
Seyler
Department of Physics, Washington University, St Louis, Missouri 63130, USA.
Vy
V
Tran
Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, USA.
Yichen
0000000288527557
Y
Jia
Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089, USA.
Huan
H
Zhao
Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089, USA.
Han
H
Wang
Department of Physics, Washington University, St Louis, Missouri 63130, USA.
Li
L
Yang
Department of Physics and Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195, USA.
Xiaodong
0000000303482095
X
Xu
Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511, USA.
Fengnian
000000015176368X
F
Xia