Exciton--polaritons in ternary mixed crystals

In this paper the bulk exciton polaritons in ternary mixed crystals (TMCs) are investigated in the Born--Huang approximation. The numerical results of the polariton frequencies as functions of the wave-vector and the compositions for ternary mixed crystals Al电震荡 三重混合晶体 激子 电磁学polariton, exciton, ternary mixed crystalProject supported partly by PhD Progress Foundation of Higher Education Institutions of China (Grant No~20040126003) and the Natural Science Foundation of Inner Mongol of China (Grant No~200408020101).2006-10-08In this paper the bulk exciton polaritons in ternary mixed crystals （TMCs） are investigated in the Born-Huang approximation. The numerical results of the polariton frequencies as functions of the wave-vector and the compositions for ternary mixed crystals AlxGa1-xAs, CdxZn1-xSe, and AlxGa1-xN are obtained and discussed. The new dispersion characteristics for exciton-polaritons in TMC systems are found in comparison with binary crystals. The splitting of the two branches of exciton-polariton frequencies varies nonlinearly with the composition of TMCs and has a minimum in the long-wavelength range.     

论极性晶体中Wannier激子的稳定性

本文中用作者之一过去得到的极性晶体中激子的有效哈密顿量,计算了Wannier激子的基态能量,从而得出结论:只有当电子、空穴的有效质量比在一定范围时,激子相对于离解为自由电子和空穴是稳定的。 关键词：     

The phenomenon of even bulk modes variance in a ferromagnetic A--A bilayer system

The eigenproblems of spin waves in a symmetrical ferromagnetic bilayered system with periodic boundary conditions are solved using the interface-rescaling approach (IRA). The results show that interface coupling between two sublayers would not change the excitation energy of odd bulk modes, but change excitation energy of even bulk modes. We call this peculiar phenomenon the phenomenon of even bulk mode variance (PEBMV). There are two kinds of mechanisms which cause PEBMV: phase reversal and phase translation of the magnon at the interface, corresponding, respectively, to the antiferromagnetic and ferromagnetic interface coupling cases. PEBMV embodies the selective effect of the interface on different bulk magnons.     

Self-Trapping of Acoustic Polaron in One Dimension

The ground-state energy and effective mass of an acoustic polaron in one dimension are calculated by using an electron-longitudinal-acoustic-phonon interaction Hamiltonian derived here. The self-trapping of the acoustic polaron is discussed. It is found that the critical coupling constant shifts toward weaker electron-phonon interaction with the increasing cutoff wave vector and the products of the critical coupling constant by the cutoff wave vector tend to a certain value. The self-trapping of acoustic polarons in one dimension is easier to be realized than that in three- and two-dimensional systems. The self-trapping transition of acoustic polarons is expected to be observed in the one dimensional systems of alkali halides and wide-band-gap semiconductors.