April 21h -Thrusday- 12:10
"Dispersive forces and spontaneous emission in non-trivial situations"
Carlos Farina(UFRJ, Brasil)
The presence of a body in the vicinities of an atomic system may change its radiative properties, particularly its atomic energy levels and natural linewidths. The atomic level shifts give rise to dispersive forces between the atom and the body, while the change on the atomic natural linewidths modifies the spontaneous emission (SE) rate of the atom, the so called Purcell effect. In the first part of the talk, after a historical survey of dispersive interactions, including its connection to the Casimir effect, we show how to compute the non-retarded interaction between an atom and a conducting surface. After introductory examples, we discuss the dispersive interaction in less trivial geometries like an atom-disk setup and an atom close to a conducting plane with a hole (where repulsive forces appear). Then, we discuss retardation effects and, as an application, we compute the dispersive interaction between an atom and a graphene sheet under an external magnetic field B. We use the large magneto optical response of graphene to control the interaction by an external agent. In the second part of the talk, after a brief survey of the SE history, we discuss some aspects of the Purcell effect: (i) suppression of the Purcell effect due to a plasmonic cloaking device, (ii) enhancement of the Purcell effect for an atom near a host dielectric semi-infinite medium with metallic inclusions (in percolation), and (iii) control of the Purcell effect for an atom in the presence of a grapheme-coated substrate under the influence of an external B.
Facultad de CienciasSeminario de Física Teórica Universidad de Zaragoza