Control of Excitons and Quantum Emitters in Two-Dimensional Materials

Abstract

Layered two-dimensional materials have emerged as promising platforms for compact solid-state devices due to their easy formation of nanometer-thick heterostructures and integration into various photonic circuits. Recently, single-photon emitters have been identified in an insulating hexagonal boron nitride (hBN) and semiconducting transition metal dichalcogenides (TMDs). In spite of the unique characteristics of these emitters, they suffer from large inhomogeneous distribution because of their proximity to the surface and external environment, limiting practical applications and identification of their origins. This thesis tackles the problem by applying external strain to control the emission energy of quantum emitters in hBN. Photophysical studies at cryogenic temperature show the coupling efficiency of different phonon modes to the quantum emitters in hBN, and a correlation between the local strain and localized exciton energy in TMDs. In addition, a strain gradient applied by a nanoscale tip modulates the local band structure of a suspended monolayer TMDs to funnel excitons in arbitrary directions. The active control of quantum emitters and excitons presented in the thesis opens up a new possibility for realizing large-scale quantum and excitonic devices.