Spectral-density polynomial expansion for two-particle Green's function in BdG framework

We develop an effcient numerical method on the basis of the spectral-density polynomial expansion to calculate two particle Green's functions in Bogoliubov-de Gennes framework for inhomogeneous superconducting systems. Our method allows systematic evaluation such as spin or charge susceptibility, nuclear magnetic relaxation rate, optical or thermal conductivity even in magnetic fields. In addition, its effciencybecomes remarkable in large-scale parallel performance.