发表机构
University of Exeter; De La Salle University; Teracan Ltd（埃克塞特大学; 德拉萨大学; 泰拉肯有限公司）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文通过横向电场调控锯齿形石墨烯纳米带的能隙，实现太赫兹范围内可调谐的光学跃迁，并利用圆光电流效应和范霍夫奇点增强辐射复合，为紧凑型太赫兹发射器提供新途径。
AI 中文摘要
我们展示了施加于锯齿形石墨烯纳米带的横向电场能够打开一个能隙，其能量可在太赫兹（THz）范围内调谐。该电场破坏了纳米带的反射对称性，从而允许在无场时被禁止的光学跃迁发生。平行于和垂直于纳米带偏振的跃迁的相对强度强烈依赖于激发频率，并在某一特定频率下变得相等。在此频率下，每种螺旋度仅选择性地激发两个场致边缘态谷之一中的载流子，且对于相反的螺旋度，所选择的谷会反转。由于这种激发发生在谷最小值之外，光激发载流子具有有限的群速度，从而产生圆光电流响应。范霍夫奇点增强了带边处的辐射复合，为紧凑型可调谐太赫兹发射器提供了一条途径。
英文摘要
We show that a transverse electric field applied to a zigzag graphene nanoribbon opens a band gap whose energy can be tuned through the terahertz (THz) range. The field breaks the reflection symmetry of the ribbon, allowing optical transitions that are forbidden in its absence. The relative strengths of transitions polarized parallel and transverse to the ribbon depend strongly on excitation frequency and become equal at a particular frequency. At this frequency, each helicity selectively excites carriers in only one of the two field-induced edge-state valleys, with the selected valley reversed for the opposite helicity. Since this excitation occurs away from the valley minima, the photoexcited carriers have finite group velocity, giving rise to a circular photogalvanic response. Van Hove singularities enhance radiative recombination at the band edge, providing a route towards compact, tunable THz emitters.
Comments10 pages, 9 figures
