The Casimir Effect In Atoms-microcavities Coupling System

The Casimir effect can be subdivided into three categories: the static Casimir effect,the dynamical Casimir effect and the Casimir-Polder force.Although they are described from different perspectives,their essence is the macroscopic quantum effect originating from the vacuum fluctuations of the electromagnetic field.The theory of the Casimir effect has attracted much attention,since it is widely applied to atomic physics,cavity quantum electrodynamics,condensed matter physics,physical chemistry,or even astrophysics.Considering the Casimir effect has important research value in many fields,we study the Casimir effect in atoms-microcavities coupling system.Firstly,we study the dynamical Casimir-Polder force between atomic ensemble and semi-infinite waveguides.Using the collective excitation operator and Holstein-Primakoff transform to simplify the Hamiltonian of the system,the second-order energy shift of the system can be derived by perturbation theory and iterative method under the Heisenberg representation.And on the basis of that,we obtain the analytical expression of the dynamical Casimir-Polder force between an atom and a semi-infinite waveguide.The evolution of the dynamical Casimir-Polder force between the atom and the conducting plate with time is studied by numerical simulation.Similarly,we also analyze the influence of different parameters on the dynamical Casimir-Polder force.This work provides a theoretical basis for the experimental detection of the dynamical Casimir-Polder force in waveguides.Secondly,we analyze the dynamical Casimir-Polder force in a dissipative cavity coupled with a two-level atom.The quantized form of electromagnetic field is derived by using Fox-Li quasi-mode theory.Based on the interaction term of the Hamiltonian of the system,the concrete form of the dynamical Casimir-Polder force can be obtained by solving the second-order energy shift of the system.Through numerical simulation,the evolution of the dynamical Casimir-Polder force between the atom and the cavity wall is analyzed.Furthermore,we also consider the effect of cavity dissipation on the dynamical Casimir-Polder force.Our results have a certain reference value to regulating or eliminating the influence of the dynamical Casimir-Polder force on micro-nano devices in the experiment.Finally,the dynamical Casimir effect in a system with nonlinear coupling between a two-level atom and a single-mode cavity field is considered.According to the Hamiltonian of the system,the time evolution operator of the system can be gained through representation transformation.Therefore,we can obtain the analytical expression of the expected number of photons generated by the dynamical Casimir effect.We analyze the influence of nonlinear coupling and the energy dissipation of the cavity on the dynamical Casimir effect through numerical simulation.This work offers a new situation for detecting dynamical Casimir effect by atoms in the experiment,that is,considering the nonlinear coupling between atoms and cavity field,which has certain research value.