title: Carbon kagome lattice and orbital-frustration-induced metal-insulator transition for optoelectronics.
abstract: A three-dimensional elemental carbon kagome lattice, made of only fourfold-coordinated carbon atoms, is proposed based on first-principles calculations. Despite the existence of 60° bond angles in the triangle rings, widely perceived to be energetically unfavorable, the carbon kagome lattice is found to display exceptional stability comparable to that of C(60). The system allows us to study the effects of triangular frustration on the electronic properties of realistic solids, and it demonstrates a metal-insulator transition from that of graphene to a direct gap semiconductor in the visible blue region. By minimizing s-p orbital hybridization, which is an intrinsic property of carbon, not only the band edge states become nearly purely frustrated p states, but also the band structure is qualitatively different from any known bulk elemental semiconductors. For example, the optical properties are similar to those of direct-gap semiconductors GaN and ZnO, whereas the effective masses are comparable to or smaller than those of Si.
authors.affiliation: Department of Physics, Applied Physics, and Astronomy Rensselaer Polytechnic Institute, Troy, New York, 12180, USA and Department of Physics, Xiangtan University, Xiangtan, Hunan 411105, People's Republic of China.
authors.forename: Yuanping
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Physics, Applied Physics, and Astronomy Rensselaer Polytechnic Institute, Troy, New York, 12180, USA.
authors.forename: Y Y
authors.initials: YY
authors.lastname: Sun
authors.affiliation: Department of Physics, Applied Physics, and Astronomy Rensselaer Polytechnic Institute, Troy, New York, 12180, USA.
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Physics, Applied Physics, and Astronomy Rensselaer Polytechnic Institute, Troy, New York, 12180, USA.
authors.forename: D
authors.initials: D
authors.lastname: West
authors.affiliation: Department of Physics, Xiangtan University, Xiangtan, Hunan 411105, People's Republic of China.
authors.forename: Yuee
authors.initials: Y
authors.lastname: Xie
authors.affiliation: Department of Physics, Xiangtan University, Xiangtan, Hunan 411105, People's Republic of China.
authors.forename: J
authors.initials: J
authors.lastname: Zhong
authors.affiliation: Department of Physics, Applied Physics, and Astronomy Rensselaer Polytechnic Institute, Troy, New York, 12180, USA.
authors.forename: V
authors.initials: V
authors.lastname: Meunier
authors.affiliation: Department of Physics, University of California at Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Marvin L
authors.initials: ML
authors.lastname: Cohen
authors.affiliation: Department of Physics, Applied Physics, and Astronomy Rensselaer Polytechnic Institute, Troy, New York, 12180, USA.
authors.forename: S B
authors.initials: SB
authors.lastname: Zhang