Sobre o controle dos efeitos do vácuo quântico por meio de condições de contorno

Abstract

In this dissertation, we trace a revision of the theory of low-energy quantum electrodynamics (QED) framework required to discuss and understand certain quantum vacuum effects. To this end, we first review classical electrodynamics and the formalism of Green dyadics, and then introduce the quantization of the electromagnetic field. Once these concepts are established, we provide a brief historical overview of QED, highlight the essential differences and similarities between the classical and quantum concepts of vacuum, and discuss some effects associated with the latter, such as the Casimir–Polder interaction, the static and dynamic Casimir effects, and the Purcell effect. A conceptual understanding of quantum vacuum effects is fundamental for establishing mechanisms to control them, which may be useful, for instance, in the design of optomechanical devices at micro- and nanometric scales. The focus of this dissertation is the control of certain vacuum effects achieved through external agents to the system, in particular via the manipulation of the boundary conditions satisfied by the radiation-field modes imposed by bodies in the vicinity of the system. We describe in great detail control mechanisms in spontaneous emission processes—namely, the Purcell effect—and in resonant energy transfer (RET), referred to throughout this work as the Andrews effect. In particular, we show that RET can be anisotropic when the atoms under consideration are placed near anisotropic planar surfaces, and we explore in detail the case in which such a surface is a phosphorene sheet, a two-dimensional material obtained from black phosphorus. In this context, we demonstrate that controlling the optical properties of phosphorene through mechanical strain can be an efficient tool for laboratory control of RET. We conclude the dissertation with some final remarks on the subject and by outlining possible perspectives and future developments stemming from this work.