四次非谐势下的能隙呼吸子和三次非谐势的影响

在局域非简谐近似(LAA)和旋转波近似(RWA)下,研究具有K2-K3-K4相互作用势的一维双原子链晶格振动的能隙呼吸子.数值计算得到以重原子为中心的对称呼吸子(HS模)振动图像,特别是不同三次非谐势的HS模振动图像.结果表明,一维K2-K3-K4双原子链中能隙呼吸子的HS模,一般只存在于四次软非简谐势(soft anharmonicity)的情况下.三次非谐势对局域振动模有显著的影响.当三次非谐势由零变为非零,轻原子的振动明显增强;随着三次非谐势的进一步增大,轻原子的振动又很快减弱.同时,DGB中心重原子的振幅随三次非谐势的变化不明显.

THE GAP BREATHERS WITH QUARTIC ANHARMONICITY AND THE EFFECTS OF CUBIC ANHARMONICITY

The discrete gap breathers(DGBs) in an one-dimensional diatomic chain with K_2-K_3-K_4 potential are studied.The analytical investigation of heavy-particle centered symmetric mode(HS mode) is implemented using the rotating-wave approximation(RWA) and local anharmonicity approximation(LAA).The effects of K_3 nonlinearity are examined especially.For various values of cubic anharmonicity,the DGB profiles are obtained for HS mode.The DGBs profiles are sensitive to K_3 nonlinearity.As K_3 increases from zero to a nonzero value,the amplitude of the central heavy particle does not change very much.But,the amplitude of its adjacent light and heavy particles becomes larger than the amplitude with zero K_3.Increasing the cubic anharmonicity further causes the DGB amplitude to decrease.In the meantime,increasing the cubic anharmonicity does not change the central heavy-particle amplitude very much.