磁场引发石墨烯从金属态到绝缘态的相变

Magnetic field induced metal-insulator phase transition in graphene

基于哈伯德模型,用微扰法计算磁场中石墨烯从金属态到绝缘态相变的临界值.研究发现,加入强磁场后,由于发生了量子霍尔效应,石墨烯的电子态和空穴态在零能级发生简并,因此零能级只能容纳1个电子,另一电子只能占据更高的朗道能级,这相当于增加了电子之间的相互作用能.磁场增大了电子之间的相互作用能,引起石墨烯从金属态向绝缘态的相变.

We calculate the critical value of condensed composite particles in graphene for metal-insulator phase transition in a magnetic field by using perturbation method based on the Hubbard model. We find that since the quantum Hall effect（ QHE） occurs in high magnetic fields,the electron state and the hole state of graphene degenerate at zero energy level. Thus the lowest Landau level could only accommodate one electron and the other electron has to go to a higher Landau level. This is equivalent to increasing the interaction energy between electrons.The interaction energy increases due to the magnetic field,which induces the metal-insulator phase transition in graphene.