Tailoring Topological Transitions of Anisotropic Polaritons by Interface Engineering in Biaxial Crystals

Abstract

Polaritons in polar biaxial crystals with extreme anisotropy offer a promising route to manipulate nanoscale light−matter interactions. The dynamic modulation of their dispersion is of great significance for future integrated nano-optics but remains challenging. Here, we report tunable topological transitions in biaxial crystals enabled by interface engineering. We theoretically demonstrate such tailored polaritons at the interface of heterostructures between graphene and α-phase molybdenum trioxide (α-MoO 3 ). The interlayer coupling can be modulated by both the stack of graphene and α-MoO 3 and the magnitude of the Fermi level in graphene enabling a dynamic topological transition. More interestingly, we found that the wavefront transition occurs at a constant Fermi level when the thickness of α-MoO 3 is tuned. Furthermore, we also experimentally verify the hybrid polaritons in the graphene/α-MoO 3 heterostructure with different thicknesses of α-MoO 3 . The interface engineering offers new insights into optical topological transitions, which may shed new light on programmable polaritonics, energy transfer, and neuromorphic photonics.

Doping-driven topological polaritons in graphene/α-MoO3 heterostructures

“…Note added in proof: While preparing this manuscript, two related theoretical and experimental studies on the tuning of highly anisotropic phonon polaritons in graphene and α-MoO 3 vdW structures were reported 41,42 .…”

Surface plasmons induce topological transition in graphene/α-MoO3 heterostructures

“…Final note: the authors became aware of the following relevant works by Álvarez-Pérez et al 32 ; Bapat et al 33 ; Hu et al 34 ; and Zeng et al 35 after completion of this work.…”

Near-field optical characterization of atomic structures and polaritons in twisted two-dimensional materials

“…Zeng 等人通过模拟计算发现在石墨烯和 α-MoO 3 堆叠的异质界面结构中， 调节石 墨烯费米能级和 α-MoO 3 的厚度分别可以实现杂化极化激元的椭圆和双曲线之间 的转变 [84] 。同年，Hai Hu 等人在实验上实现了通过改变费米能来调控"石墨烯 /α-MoO 3 /衬底" 结构的极化激元的拓扑转变 [85] 。 该团队还发现， 在红外光 910 cm -1 的波数下，石墨烯/α-MoO 3 结构在 Au 衬底上比在 SiO 2 衬底上更容易实现调控， 即更低的费米能即可实现双曲线到椭圆的极化激元的转变。 图 10 转角双层 α-MoO 3 的声子极化激元的拓扑转变。 [83] (f-i)和(n-q)对应计算的电场分布 z 分量的实数部分，Re(Ez)。(出自文献 [83] ，已获得 授权)…”