Investigations of low-dimensional emitter system by dynamic strain platform

Abstract

Two-dimensional transitional metal dichalcogenides (2D TMDs) and zero-dimensional quantum dots (QDs) are among the most representative low-dimensional emitter systems, with one or three dimensions on nano-scale. Both of them exhibit potential for (quantum) optical applications. Analog to the electric field and magnetic field, strain is a powerful probe to detect the physics of the emitter systems. The reduced dimension renders strain tuning more applicable to deepen the understanding and tune their properties. Previous researches demonstrate that strain can change the distance of particles or/and the symmetry. Based on this, we conduct some investigations: first, we detect the responses of monolayer WSe2 to biaxial in-plane strain. Generally, all the helicities of excitons and trions are related to the scattering process. In our observation, the decreases of exciton circular helicities in WSe2 and MoSe2 are associated with their e-h exchange interactions. The helicity of trion in MoSe2 is almost intact, and a phenomenological rate equation model is developed to describe the decrease of trions in WSe2, which agrees with our observation well. Our findings provide a new strategy to tune the read-in/read-out in TMDs-based memory devices. Second, we focus on the responses of WSe2 to uniaxial strain. We identify fine structures of neutral exciton in polarization-dependent photoluminescence spectroscopy. The nonlinear evolutions, in terms of amplitude and phase, with an active uniaxial strain are interpreted by the interaction of wavefunction with strain. Though these two bulk strain-tuning platforms hold the potential for sophisticated emitter systems, a more versatile strain-tuning platform is needed. In the last section of this work, a 2-leg MEMS strain-tuning platform is fabricated and then integrated with a QDs-embedded membrane. We resolve the position-dependent anisotropic strain on the strain-tuning platform and compare the opposite responses of positive and negative trions to the same strain. Our observation agrees well with the previous pseudo-potential/configuration interaction calculations. Notably, the 2-leg strain platform applies to 2D TMDs. These findings act as some helpful attempts to deepen the understanding of low-dimensional emitter systems. In some ongoing work, we get a prototype as a more versatile strain-tuning platform. We envision this platform can add a degree of freedom for the integrated photonic circuits.