Valley Pseudospin with a Widely Tunable Bandgap in Doped Honeycomb BN Monolayer.
Valleytronics is a promising paradigm to explore the emergent degree of freedom for charge carriers on the energy band edges. Using ab initio calculations, we reveal that the honeycomb boron nitride (h-BN) monolayer shows a pair of inequivalent valleys in the vicinities of the vertices of hexagonal Brillouin zone even without the protection of the C3symmetry. The inequivalent valleys give rise to a 2-fold degree of freedom named the valley pseudospin. The valley pseudospin with a tunable bandgap from deep ultraviolet to far-infrared spectra can be obtained by doping h-BN monolayer with carbon atoms. For a low-concentration carbon periodically doped h-BN monolayer, the subbands with constant valley Hall conductance are predicted due to the interaction between the artificial superlattice and valleys. In addition, the valley pseudospin can be manipulated by visible light for high-concentration carbon doped h-BN monolayer. In agreement with our calculations, the circularly polarized photoluminescence spectra of the B0.92NC2.44sample show a maximum valley-contrasting circular polarization of 40% and 70% at room temperature and 77 K, respectively. Our work demonstrates a class of valleytronic materials with a controllable bandgap.
Zhigang
0000-0002-8355-6498
Z
Song
Ziwei
0000-0002-2987-7186
Z
Li
Center for Programmable Materials, School of Materials Science and Engineering, Nanyang Technological University , Singapore 639798.
Hong
H
Wang
Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.|Collaborative Innovation Center of Quantum Matter , Beijing 100871, China.
Xuedong
X
Bai
Institute of Physics, Chinese Academy of Sciences , Beijing 100190, China.
Wenlong
W
Wang
Honglin
H
Du
Sunquan
S
Liu
Changsheng
C
Wang
Jingzhi
J
Han
Yingchang
Y
Yang
Center for Programmable Materials, School of Materials Science and Engineering, Nanyang Technological University , Singapore 639798.
Zheng
0000-0002-8825-7198
Z
Liu
Collaborative Innovation Center of Quantum Matter , Beijing 100871, China.
Jing
J
Lu
Collaborative Innovation Center of Quantum Matter , Beijing 100871, China.
Zheyu
0000-0001-5780-0728
Z
Fang
Collaborative Innovation Center of Quantum Matter , Beijing 100871, China.
Jinbo
J
Yang
BNC monolayer; Valleytronics; ab initio calculation; photoluminescence spectra; pseudospin; valley polarization