Gated graphene superlattices, where in-plane variations in the potential-energy profile are introduced with a periodic patterning of the gate electrode or dielectric, provide new opportunities for tailoring the electronic and optical properties of two-dimensional materials. Here we present a numerical study of the optical transitions between minibands derived from the same energy band (conduction or valence) in these systems. Giant absorption peaks at voltage-tunable THz frequencies are obtained, associated with van Hove singularities in the joint density of states of select pairs of minibands. Furthermore, we describe the possibility of interminiband THz gain in the same systems under external carrier injection, resulting from a local population inversion at specific symmetry points of the mini-Brillouin zone, even in the absence of a global inversion. These results highlight the great potential of engineered graphene superlattices for THz optoelectronic device applications, including modulators, tunable photodetectors, and lasers.

中文翻译：

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石墨烯横向超晶格中的超微带光学跃迁

门控石墨烯超晶格通过栅电极或电介质的周期性图案引入势能曲线的面内变化，为定制二维材料的电子和光学特性提供了新的机会。在这里，我们对来自这些系统中相同能带（导数或价态）的微带之间的光学跃迁进行了数值研究。获得了在电压可调的THz频率处的巨大吸收峰，这些峰与选择的微带对的状态联合密度中的van Hove奇点相关。此外，我们描述了在外部载波注入下相同系统中跨频带THz增益的可能性，这是由于微型布里渊区的特定对称点处的局部种群反转而引起的，即使没有全局反转 这些结果凸显了工程石墨烯超晶格在太赫兹光电器件应用（包括调制器，可调光探测器和激光器）中的巨大潜力。