Department of Physics, University of Texas, Austin, TX 78712, USA.
Proc Natl Acad Sci U S A. 2011 Jul 26;108(30):12233-7. doi: 10.1073/pnas.1108174108. Epub 2011 Jul 5.
A moiré pattern is formed when two copies of a periodic pattern are overlaid with a relative twist. We address the electronic structure of a twisted two-layer graphene system, showing that in its continuum Dirac model the moiré pattern periodicity leads to moiré Bloch bands. The two layers become more strongly coupled and the Dirac velocity crosses zero several times as the twist angle is reduced. For a discrete set of magic angles the velocity vanishes, the lowest moiré band flattens, and the Dirac-point density-of-states and the counterflow conductivity are strongly enhanced.
当两个周期性图案的副本叠加有相对扭转时，会形成莫尔图案。我们研究了扭曲双层石墨烯系统的电子结构，表明在其连续的狄拉克模型中，莫尔图案的周期性导致了莫尔布洛赫带。随着扭转角的减小，两层变得更强耦合，狄拉克速度多次穿过零。对于一组离散的魔法角度，速度为零，最低的莫尔能带变平，狄拉克点态密度和逆流电导率得到了强烈增强。
