Small: plasmon superstructural surface and single-layer MoS2 photo controlled near-field energy transfer

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The rise of

two-dimensional hexagonal graphene like layered materials has promoted the great development of photoelectric properties of nano materials. Transition metal disulfides (TMDs) as typical graphene like materials also have unique physical properties optical response. Compared with graphene TMDs family is a kind of semiconductor material with natural b gap. MoS2 monolayer a member of two-dimensional TMDs family has its own unique properties such as single-layer direct b gap tunable exciton fast photoelectric response so on. Therefore it is widely used in the research development of new nano devices nano optics. On the other h in near-field optics the plasmon produced by the interaction between metal light on the surface of the medium has become an effective means to enhance control light at the micro nano scale. Plasmons can be divided into surface plasmon polaritons (SPP) local surface plasmon (LSP). LSP can not only bind enhance light in near field but also modulate the properties of light by coupling with light in different ways.

by designing the metasurface of C3 in the mode of plasmon microcavity (GSP) Fang Zheyu School of physics Peking University realized the plasmon array with strong far-field photoluminescence (PL) further coupled the array with MoS2 monolayer. In the spectral characterization of metasurface-mos2 heterostructure it was found that the near-field effect of plasmon super structure surface enhanced the fluorescence of MoS2 monolayer by more than 10 times. It is found that the energy of the two coupling fields will be transferred to the metall system. The process of energy transfer is reflected in the detection of the lifetime of MoS2 exciton in ultrafast characterization. By detecting the fast exciton process (exciton exciton dissipation process) of MoS2 in heterostructures it is found that the process is nearly three times delayed due to the energy transfer which is close to the decay time of the plasmon metal; on the contrary the detection of the slow process (the radiation lifetime of the exciton itself) shows that the exciton radiation process is accelerated by the enhancement of the near-field of the plasmon the slow process is large The result of large shortening. Due to the effective energy transfer the exciton emission in MoS2 becomes actively tunable. What is interesting about

is that in the process of energy transfer between plasmon PL MoS2 fluorescence PL both of them are coupled as oscillators to renormalize broaden the energy level of MoS2. The corresponding physical mechanism is that the PL of the plasmon hyperstructure surface is the radiative luminescence of the electron of gold (AU) in the transition from SP b to d b while the inner metal is a continuous energy level. The PL coupling of the two makes the emission level of MoS2 renormalized then exped into a series of energy levels. The theoretical results show that the renormalized energy levels correspond to the eigenvalues of a series of normal modes generated by the general solution (EGS) of the coupling equation. In the

experiments the excited excitons will be filled from low to high according to the new coupling energy levels. Under the condition of changing the excitation power of the light source in terms of radiation energy (wavelength) the PL spectrum of the heterojunction shows that the fluorescence peak is redder than that of MoS2 monolayer under low power excitation when the excitation power increases the fluorescence peak gradually shifts blue which finally shows the comprehensive effect of the downward competitive transition of excitons from high low energy levels; in terms of radiation intensity the PL of the heterojunction changes with the increase of excitation power The change of excitation power shows a nonlinear positive correlation growth from slow to fast the phenomenon of unsaturation appears that is the dynamic equilibrium of the upward transition downward emission of excitons due to the saturation of energy levels. Finally the emission energy (wavelength) of the system can be controlled by the excitation conditions in the range of tens of nanometers it always presents the unsaturated transition radiation.

so far we have demonstrated a feasible method to study the interaction between light matter in two-dimensional materials. Not only the near-field energy transfer system of plasmon superstructure surface MoS2 single-layer fluorescence has been built in practice so that the radiation ability of PL fluorescence of the system can be actively adjusted the equation corresponding to the coupling process of the oscillator system is established. The theoretical results show that a series of eigensolutions generated by the general solution (EGS) are exactly the results of the energy level renormalization of MoS2. More importantly the normal mode of the general mathematical solution of the oscillator coupling model proposed in this work solves the problem that can not be solved by the energy b theory from the perspective of quantum perturbation that is the calculation of the energy b modulation result caused by the interaction between two sets of energy bs of solid enriches the research content of the solid energy b theory theoretically. This theoretical practical method is not only applicable to the system studied in this paper but also applicable to other similar coupling systems which provides new ideas methods for the preparation of nano photonic devices in optical control system. The results of

were published in small (DOI: 10.1002 / small. 202003539).

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