Moorsom Timothy, McCauley Mairi, Nizamuddin Bin Muhammad Mustafa Ahmad, Ramadan Sami, Burton Joel, Sasaki Satoshi, MacLaren Donald A, Petrov Peter K
School of Chemical and Process Engineering, University of Leeds, Leeds, LS2 9JT, UK.
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK.
Sci Rep. 2024 Dec 28;14(1):30927. doi: 10.1038/s41598-024-81488-7.
Topological Insulators (TIs) are promising platforms for Quantum Technology due to their topologically protected surface states (TSS). Plasmonic excitations in TIs are especially interesting both as a method of characterisation for TI heterostructures, and as potential routes to couple optical and spin signals in low-loss devices. Since the electrical properties of the TI surface are critical, tuning TI surfaces is a vital step in developing TI structures that can be applied in real world plasmonic devices. Here, we present a study of BiSe/graphene heterostructures, prepared using a low-cost transfer method that reliably produces mono-layer graphene coatings on BiSe flakes. Using both Raman spectroscopy and electron energy loss spectroscopy (EELS), we show that the graphene layer redshifts the energy of the π plasmon mode in BiSe, creating a distinct surface plasmon that differs significantly from the behaviour of a TI-trivial insulator boundary. We demonstrate that this is likely due to band-bending and electron transfer between the TI surface and the graphene layer. Based on these results, we outline how graphene overlayers can be used to create tuneable, stable plasmonic materials based on topological insulators.
拓扑绝缘体（TIs）因其拓扑保护表面态（TSS）而成为量子技术的有前景的平台。拓扑绝缘体中的等离子体激元尤其有趣，既作为表征TI异质结构的一种方法，又作为在低损耗器件中耦合光信号和自旋信号的潜在途径。由于TI表面的电学性质至关重要，调整TI表面是开发可应用于实际等离子体器件的TI结构的关键一步。在此，我们展示了对BiSe/石墨烯异质结构的研究，该结构采用低成本转移方法制备，能在BiSe薄片上可靠地生成单层石墨烯涂层。通过拉曼光谱和电子能量损失谱（EELS），我们表明石墨烯层使BiSe中π等离子体激元模式的能量发生红移，产生了一种与TI平凡绝缘体边界行为显著不同的独特表面等离子体激元。我们证明这可能是由于TI表面与石墨烯层之间的能带弯曲和电子转移。基于这些结果，我们概述了如何利用石墨烯覆盖层来创建基于拓扑绝缘体的可调谐、稳定的等离子体材料。
