Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2010 Apr 16;104(15):156803. doi: 10.1103/PhysRevLett.104.156803. Epub 2010 Apr 15.
Electron interactions in undoped bilayer graphene lead to an instability of the gapless state, "which-layer" symmetry breaking, and energy gap opening at the Dirac point. In contrast with single-layer graphene, the bilayer system exhibits instability even for an arbitrarily weak interaction. A controlled theory of this instability for realistic dynamically screened Coulomb interactions is developed, with full account of the dynamically generated ultraviolet cutoff. This leads to an energy gap that scales as a power law of the interaction strength, making the excitonic instability readily observable.
在未掺杂双层石墨烯中，电子相互作用导致能隙消失状态的不稳定性、“哪一层”对称性破缺以及在狄拉克点处能隙的打开。与单层石墨烯不同，即使是在任意弱相互作用的情况下，双层体系也表现出不稳定性。本文针对现实的动态屏蔽库仑相互作用，发展了一种对这种不稳定性的可控理论，充分考虑了动态产生的紫外截止。这导致能隙按相互作用强度的幂律缩放，使激子不稳定性很容易被观察到。
