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Magnetic gap opening in rhombohedral-stacked multilayer graphene from first principles

机译:基于第一原理的菱面体堆叠多层石墨烯的磁隙开口

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摘要

We investigate the occurrence of magnetic and charge density wave instabilities in rhombohedral-stacked multilayer (three to eight layers) graphene by first principles calculations including exact exchange. Neglecting spin polarization, an extremely flat surface band centered at the special point K of the Brillouin zone occurs at the Fermi level. Spin polarization opens a gap in the surface state by stabilizing an antiferromagnetic state. The top and the bottom surface layers are weakly ferrimagnetic in-plane (net magnetization smaller than 10~(-3)μ_B) and are antiferromagnetic coupled to each other. This coupling is propagated by the out-of-plane antiferromagnetic coupling between the nearest neighbors. The gap is very small in a spin-polarized generalized gradient approximation, while it is proportional to the amount of exact exchange in hybrid functionals. For trilayer rhombohedral graphene it is 38.6 meV in PBE0, in agreement with the 42 meV gap found in experiments. We study the temperature and doping dependence of the magnetic gap. At electron doping of n ~ 7 x 10~11 cm~(-2) the gap closes. Charge density wave instabilities with 3~(1/2) x3~(1/2) periodicity do not occur.
机译:我们通过包括精确交换在内的第一原理计算研究了菱面体堆叠多层(三层至八层)石墨烯中磁波和电荷密度波不稳定性的发生。忽略自旋极化,在费米能级处出现一个以布里渊区的特殊点K为中心的极其平坦的表面带。自旋极化通过稳定反铁磁状态而在表面状态中打开了一个缺口。顶部和底部表面层是弱铁磁平面内(净磁化强度小于10〜(-3)μ_B),并且彼此反铁磁耦合。该耦合通过最近邻居之间的平面外反铁磁耦合传播。在自旋极化广义梯度近似中,该间隙非常小,而与混合功能中的精确交换量成正比。对于三层菱面体石墨烯,PBE0中为38.6 meV,与实验中发现的42 meV缺口相符。我们研究了磁隙的温度和掺杂依赖性。在电子掺杂为n〜7 x 10〜11 cm〜(-2)时,间隙闭合。不会发生周期为3〜(1/2)x3〜(1/2)的电荷密度波不稳定性。

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  • 来源
    《Physical review》 |2017年第7期|075422.1-075422.8|共8页
  • 作者单位

    CNRS, UMR 7590 and Sorbonne Universités, UPMC Univ Paris 06, IMPMC-Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie, 4 place Jussieu, F-75005, Paris, France;

    CNRS, UMR 7590 and Sorbonne Universités, UPMC Univ Paris 06, IMPMC-Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie, 4 place Jussieu, F-75005, Paris, France;

    Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale Aldo Moro 5,1-00185 Rome, Italy,Graphene Labs, Fondazione Istituto Italiano di Tecnologia, Via Morego, 1-16163 Genoa, Italy;

    CNRS, UMR 7590 and Sorbonne Universités, UPMC Univ Paris 06, IMPMC-Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie, 4 place Jussieu, F-75005, Paris, France;

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