Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
J Phys Condens Matter. 2011 Apr 20;23(15):155602. doi: 10.1088/0953-8984/23/15/155602. Epub 2011 Apr 1.
A sufficiently strong Coulomb interaction may open an excitonic fermion gap and thus drive a semi-metal-insulator transition in graphene. In this paper, we study the Eliashberg theory of excitonic transition by coupling the fermion gap equation self-consistently to the equation of the vacuum polarization function. Including the fermion gap into the polarization function increases the effective strength of the Coulomb interaction because it reduces the screening effects due to the collective particle-hole excitations. Although this procedure does not change the critical point, it leads to a significant enhancement of the dynamical fermion gap in the excitonic insulating phase. The validity of the Eliashberg theory is justified by showing that the vertex corrections are suppressed at the large N limit.
足够强的库仑相互作用可能会打开激子费米能隙，从而驱动石墨烯的半导体-绝缘体转变。在本文中，我们通过将费米能隙方程自洽地耦合到真空极化函数方程，研究了激子跃迁的 Eliashberg 理论。将费米能隙纳入极化函数会增加库仑相互作用的有效强度，因为它会降低由于集体粒子-空穴激发引起的屏蔽效应。尽管这一过程不会改变临界点，但它会导致激子绝缘相中动力学费米能隙的显著增强。通过表明在大 N 极限下顶点修正被抑制，证明了 Eliashberg 理论的有效性。
