Dong Y, Sun Z, Phinney I Y, Sun D, Andersen T I, Xiong L, Shao Y, Zhang S, Rikhter Andrey, Liu S, Jarillo-Herrero P, Kim P, Dean C R, Millis A J, Fogler M M, Bandurin D A, Basov D N
Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA.
Department of Physics, Columbia University, New York, NY, USA.
Nat Commun. 2025 Apr 24;16(1):3861. doi: 10.1038/s41467-025-58953-6.
Electrons in low-dimensional materials driven out of equilibrium by a strong electric field exhibit intriguing effects that have direct analogues in high-energy physics. In this work we demonstrate that two of these effects can be observed in graphene, leading to relevant implications for light-matter interactions at the nanoscale. For doped graphene, the Cherenkov emission of phonons caused by the fast flow of out-of-equilibrium electrons was found to induce direction-dependent asymmetric plasmon damping and an unexpected generation of photocurrent. For graphene close to charge neutrality, incident infrared photons were found to disrupt the creation-recombination balance of electron-hole pairs enabled by the condensed matter version of the Schwinger effect, resulting in an excess photocurrent that we term Schwinger photocurrent. Both Schwinger and Cherenkov photocurrents are different from other known light-to-current down conversions scenarios and thus expand the family of photoelectric effects in solid state devices. Through nano-infrared imaging methodology, we provide a more comprehensive view of current-driven nonequilibrium electrodynamics in graphene.
在强电场作用下，低维材料中的电子被驱动至非平衡态，会展现出一些有趣的效应，这些效应在高能物理中有直接的类似物。在这项工作中，我们证明了在石墨烯中可以观察到其中两种效应，这对纳米尺度下的光与物质相互作用具有重要意义。对于掺杂石墨烯，发现非平衡电子的快速流动所引发的声子切伦科夫发射会导致方向依赖的不对称等离激元阻尼以及意外的光电流产生。对于接近电荷中性的石墨烯，发现入射红外光子会破坏由凝聚态施温格效应实现的电子 - 空穴对的产生 - 复合平衡，从而产生一种我们称为施温格光电流的过量光电流。施温格光电流和切伦科夫光电流都与其他已知的光到电流下转换情形不同，因此扩展了固态器件中光电效应的范畴。通过纳米红外成像方法，我们对石墨烯中电流驱动的非平衡电动力学有了更全面的认识。
