Department of Physics and Astronomy, Hunter College of City University of New York, 695 Park Avenue, New York, NY 10065-50085, USA.
Philos Trans A Math Phys Eng Sci. 2010 Dec 13;368(1932):5431-43. doi: 10.1098/rsta.2010.0215.
Graphene nanoribbons (GNRs) in mutually perpendicular electric and magnetic fields are shown to exhibit dramatic changes in their band structure and electron-transport properties. A strong electric field across the ribbon induces multiple chiral Dirac points, closing the semiconducting gap in armchair GNRs. A perpendicular magnetic field induces partially formed Landau levels as well as dispersive surface-bound states. Each of the applied fields on its own preserves the even symmetry E(k)=E(-k) of the sub-band dispersion. When applied together, they reverse the dispersion parity to be odd, which gives E(e,k)=-E(h,-k), and mix the electron and hole sub-bands within the energy range corresponding to the change in potential across the ribbon. This leads to oscillations of the ballistic conductance within this energy range. The broken time-reversal symmetry provides dichroism in the absorption of the circularly polarized light. As a consequence, one can observe electrically enhanced Faraday rotation, since the edges of the ribbon provide formation of the substantial density of states.
在相互垂直的电场和磁场中，石墨烯纳米带（GNRs）表现出其能带结构和电子输运性质的剧烈变化。沿纳米带施加强电场会诱导出多个手性狄拉克点，从而关闭扶手椅型 GNRs 的半导体能隙。垂直磁场会诱导出部分形成的朗道能级和弥散的表面束缚态。单独施加的每个场本身都保持子带色散的偶数对称 E(k)=E(-k)。当一起施加时，它们会将色散奇偶性反转到奇数，即 E(e,k)=-E(h,-k)，并在对应于纳米带中电势变化的能量范围内混合电子和空穴子带。这导致在该能量范围内弹道电导的振荡。破坏时间反演对称性在圆偏振光的吸收中产生二色性。因此，可以观察到电增强的法拉第旋转，因为纳米带的边缘提供了大量的态密度形成。
