物理学报2017，Vol.66Issue(11)：46-53,8.DOI:10.7498/aps.66.110502
含时驱动的Dicke模型的混沌特性
Chaos propeties of the time-dependent driven Dicke model
摘要
Abstract
Now,many different approaches have been presented to study the different semi-classical models derived from the Dicke Hamiltonian,which reflect a fact that the quantum-mechanical spin possesses no direct classical analog.The Hartree-Fock-type approximation is one of the widely used approaches,with which we derive the Heisenberg equations of motion for the system and replace the operators in these equations with the corresponding expectation values.In the present paper,we investigate the role of quantum phase transition in determining the chaotic property of the timedependent driven Dicke model.The semi-classical Hamiltonian is derived by evaluating the expectation value of the Dicke Hamiltonian in a state,which is a product state of photonic and atomic coherent states.Based on the inverse of the relations between the position-momentum representation and the Bosonic creation-annihilation operators,the Hamiltonian is rewritten in the position-momentum representation and it undergoes a spontaneous symmetry-breaking phase transition,which is directly analogous to the quantum phase transition of the quantum system.In order to depict the Poincaré sections,which are used to analyze the trajectories through the four-dimensional phase space,we give the equations of motion of system from the derivatives of the semi-classical Hamiltonian for a variety of different parameters and initial conditions.According to the Dicke quantum phase transition observed from the experimental setup,we study the effect of a monochromatic non-adiabatic modulation of the atom-field coupling in Dicke model (i.e.,the driven Dicke model) on the system chaos by adjusting the pump laser intensity.The change from periodic track to chaotic figure reflects the quantum properties of the system,especially the quantum phase transition point,which is a key position for people to analyse the shift from periodic orbit to chaos.In an undriven case,the system reduces to the standard Dicke model.We discover from the Poincaré sections that the system undergoes a change from the classical periodic orbit to a number of chaotic trajectories and in the superradiant phase area,the whole phase space is completely chaotic.When the static and driving coupling both exist,the system shows rich chaotic motion.The ground state properties are mainly determined by the static coupling,while the orbit of the system is adjusted by the driving coupling.If the static coupling is greater than the critical coupling,the system displays completely chaotic images in the Poincaré sections,and the periodic orbits in the chaos can also be adjusted by the strong driving coupling.While the static coupling is less than the critical coupling,the system can also show the chaotic images by adjusting the driving coupling strength and oscillation frequency.Moreover,by tuning the oscillation frequency,the Poincaré sections may change from the classical orbits to the chaos,and back to the classical orbits in the normal phase of the system.关键词
单频非绝热调制/Dicke模型/量子混沌/庞加莱截面图Key words
a monochromatic non-adiabatic modulation/Dicke model/quantum chaos/the Poincaré section引用本文复制引用
刘妮,梁九卿..含时驱动的Dicke模型的混沌特性[J].物理学报,2017,66(11):46-53,8.基金项目
Project supported by the National Natural Science Foundation of China (Grant Nos.11404198,11275118,91430109),the Scientific and Technological Innovation Program of Higher Education Institutions in Shanxi Province (STIP),China (Grant No.2014102),the Launch of the Scientific Research of Shanxi University,China (Grant No.011151801004),and the National Fundamental Training,China (Grant No.J1103210).国家自然科学基金(批准号:11404198,11275118,91430109)、山西省高等学校科技创新项目(批准号:2014102)、山西大学科研启动金(批准号:011151801004)和国家基础科学人才培养基金(批准号:J1103210)资助的课题. （Grant Nos.11404198,11275118,91430109）
