球对称铷原子玻色-爱因斯坦凝聚中单极子模的朗道阻尼和频移

Landau damping and frequency-shift of a monopole mode in a spherical rubidium Bose-Einstein condensate

采用含时哈特里-福克-博戈留波夫近似研究球对称铷原子玻色-爱因斯坦凝聚中单极子模的朗道阻尼和频移,并用现有实验和数值模拟研究的粒子数和囚禁频率参量,解析计算了阻尼系数和频移大小及其它们的温度依赖.计算中,考虑元激发的实际弛豫及其各弛豫间的正交关系以获得阻尼和频移计算公式,把基态波函数取为高斯分布函数的一级近似以消除三模耦合矩阵元的发散.我们的计算结果与数值模拟结果和实验结果分别进行直接和间接地对比,讨论和说明了我们理论方法的合理性.

The Landau damping and frequency- shift of a monopole mode in a spherical rubidium Bose- Einstein condensate are investigated by using the Hartree- Fock- Bogoliubov approximation. The damping rate and frequency- shift magnitude and their temperature dependence are analytically calculated by using the parameters of particle number and traping frequency in the study of numerical simulation and experiment in existence. In the calculation,the practical relaxations of the elementary excitations and the orthometric relation among them are taken into account to obtain the calculation formula for damping and frequency- shift,and the first approximation of Gaussian distribution function is employed for the ground- state wavefunction to eliminate the divergence of the three- mode coupling matrix elements. Our calculation results are directly and indirectly compared with the numerical simulation ones and experimental ones,respectively. And all the comparison illustrate that our method is reasonable.