Population dynamics and phase effects in periodic level crossings

被引:67
作者
Garraway, BM
Vitanov, NV
机构
[1] Optics Section, Blackett Laboratory, Imperial College, London, SW7 2BZ, Prince Consort Road
[2] Research Institute for Theoretical Physics, University of Helsinki, Helsinki, 00014, P.O. Box 9
关键词
D O I
10.1103/PhysRevA.55.4418
中图分类号
O43 [光学];
学科分类号
070207 ; 0803 ;
摘要
We present an analytic study of the population dynamics of a two-state system interacting with an external field and subjected to periodic level crossings. We apply an evolution matrix approach to calculate the excited-state population at the crossings (the nodes) and at the antinodes. The results are expressed in terms of only two parameters: the transition probability p for a quarter period from a crossing to an antinode, and the transition probability P for a half period between two successive crossings. We find that the values of the excited-state population at the antinodes can form global (gross) structures. We show that these structures and the population dynamics as a whole are very sensitive to the initial phase phi of the frequency-modulated field, particularly in the limits phi=0 (cosine modulation) and phi=pi/2 (sine modulation). We calculate the parameters p and P by using two analytic approaches: one based on the original Landau-Zener model, and the other based on the finite Landau-Zener model. Both approaches unexpectedly lead to the same results. The notion of the global structures and the relevant parametrization in terms of p and P allow us to find various distinctive cases of population dynamics, such as population swapping, completely periodic evolution, superpositional trapping, and stepwise evolution.
引用
收藏
页码:4418 / 4432
页数:15
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