Floquet spectrum and universal dynamics of a periodically driven two-atom system

We investigate the Floquet spectrum and excitation properties of a two-ultracold-atom system with periodically driven interaction in a three-dimensional harmonic trap.The interaction between the atoms is changed by varying the s-wave scattering length in two ways,the cosine and the square-wave modulations.It is found that as the driving frequency increases,the Floquet spectrum exhibits two main features for both modulations,the accumulating and the spreading of the quasienergy levels,which further lead to different dynamical behaviors.The accumulation is associated with collective excitations and the persistent growth of the energy,while the spread indicates that the energy is bounded at all times.The initial scattering length,the driving frequency and amplitude can all significantly change the Floquet spectrum as well as the dynamics.However,the corresponding relation between them is valid universally.Finally,we propose a mechanism for selectively exciting the system to one specific state by using the avoided crossing of two quasienergy levels,which could guide preparation of a desired state in experiments.

浅谈公路工程稀浆封层施工工艺

改革开放40多年来,我国经济高速发展,面对日益增长的运输需求,公路建设规模持续扩大,交通事业取得了令人瞩目的成绩。然而,在行车荷载和自然因素的作用下,很多沥青路面在通车 2、3 年便出现了不同程度的病害,比如裂缝、车辙等。若不及时处理,极易发展为更严重的病害问题,甚至破坏路面结构,影响路面使用性能。基于此,必须重视沥青路面预防性养护施工工艺。稀浆封层技术的应用,可以有效阻止病害发展,改善路面使用性能,延长道路使用寿命。因此,开展公路养护稀浆封层技术研究具有重要意义和应用价值。