Lee H C, Choi H Y
Department of Physics and Basic Science Research Institute, Sogang University, Seoul 121-742, Korea.
J Phys Condens Matter. 2009 Nov 4;21(44):445701. doi: 10.1088/0953-8984/21/44/445701. Epub 2009 Oct 15.
Electronic Raman scattering of two-band superconductors is studied based on the time-dependent Landau-Ginzburg theory. The focus is on the possible features of the π phase shift between the two superconducting order parameters which may be realized in the Fe-pnictides. The Raman response was computed up to the Gaussian fluctuations in the functional integral formalism including the long range Coulomb interaction with the four channels of symmetric and antisymmetric combinations of the phases and amplitudes of the two order parameters. The Raman spectra is found to be composed of the quasiparticle and the phase collective mode contributions without mixing between them. The contributions from the quasiparticle and the symmetric phase collective mode (the Anderson-Bogolyubov mode) are similar to the two-band superconductors without the π phase shift. The antisymmetric phase mode (the Leggett mode) originates from the fluctuations of the relative phase of the two order parameters. It lies between twice the smaller gap and twice the larger gap and is damped by the quasiparticles. However, this mode is eliminated by the long range Coulomb interaction in the zero-wavenumber limit.
基于含时朗道-金兹堡理论研究了两带超导体的电子拉曼散射。重点关注在铁基氮化物中可能实现的两个超导序参量之间π相移的可能特征。在泛函积分形式中，包括与两个序参量的相位和振幅的对称和反对称组合的四个通道的长程库仑相互作用，计算了高达高斯涨落的拉曼响应。发现拉曼光谱由准粒子和相位集体模贡献组成，它们之间没有混合。准粒子和对称相位集体模（安德森-博戈留波夫模）的贡献类似于没有π相移的两带超导体。反对称相位模（莱格特模）起源于两个序参量相对相位的涨落。它位于较小能隙的两倍和较大能隙的两倍之间，并被准粒子阻尼。然而，在零波数极限下，这种模式被长程库仑相互作用消除。
