Glinka Yuri D, Babakiray Sercan, Johnson Trent A, Lederman David
Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506-6315, USA. Institute of Physics, National Academy of Sciences of Ukraine, Kiev 03028, Ukraine.
J Phys Condens Matter. 2015 Feb 11;27(5):052203. doi: 10.1088/0953-8984/27/5/052203. Epub 2015 Jan 23.
We report on a >100-fold enhancement of Raman responses from Bi2Se3 thin films if laser photon energy switches from 2.33 eV (532 nm) to 1.58 eV (785 nm), which is due to direct optical coupling to Dirac surface states (SS) at the resonance energy of ∼1.5 eV (a thickness-independent enhancement) and due to nonlinearly excited Dirac plasmon (a thickness-dependent enhancement). Owing to the direct optical coupling, we observed an in-plane phonon mode of hexagonally arranged Se-atoms associated with a continuous network of Dirac SS. This mode revealed a Fano lineshape for films <15 nm thick, resulting from quantum interference between surface phonon and Dirac plasmon states.
我们报道，如果激光光子能量从2.33电子伏特（532纳米）切换到1.58电子伏特（785纳米），Bi2Se3薄膜的拉曼响应会增强100倍以上，这是由于在约1.5电子伏特的共振能量下与狄拉克表面态（SS）的直接光学耦合（与厚度无关的增强）以及非线性激发的狄拉克等离子体激元（与厚度有关的增强）。由于直接光学耦合，我们观察到与狄拉克SS连续网络相关的六边形排列的硒原子的面内声子模式。对于厚度小于15纳米的薄膜，该模式呈现出法诺线形，这是表面声子和狄拉克等离子体激元态之间量子干涉的结果。
