| Title | Linear response functions respecting Ward-Takahashi identity and fluctuation-dissipation theorem within the GW approximation |
| Authors | Li, Hui Sun, Zhipeng Su, Yingze Lin, Haiqing Huang, Huaqing Li, Dingping |
| Affiliation | Peking Univ, Sch Phys, Beijing 100871, Peoples R China Beijing Computat Sci Res Ctr, Beijing 100193, Peoples R China |
| Keywords | COVARIANT GAUSSIAN APPROXIMATION GREENS-FUNCTION DENSITY |
| Issue Date | 6-Feb-2023 |
| Publisher | PHYSICAL REVIEW B |
| Abstract | Fundamental equalities, such as the Ward-Takahashi identity (WTI) and the fluctuation-dissipation theorem (FDT), are important in the calculation of the response functions, which are defined as the variations of physical quantities with respect to the external sources. In this paper, the formalism of calculating the response functions according to their original definitions is presented, based on the generalized GW (GGW) method which was developed for the electronic systems including spin-dependent interaction. This formalism automatically ensures the FDT, and is theorectically proved to respect the WTI. By contrast, the commonly used random phase approximation (RPA) within the GGW method violates both the WTI and the FDT, and the Bethe-Salpeter equation (BSE) satisfies the WTI but does not fulfill the FDT. The validity of this methodology is demonstrated on the two-dimensional one-band Hubbard model, and the results show that our formalism makes significant improvements over the RPA formula. Due to the similar computational cost to the BSE, our formalism is expected to be applied to realistic materials. |
| URI | http://hdl.handle.net/20.500.11897/671981 |
| ISSN | 2469-9950 |
| DOI | 10.1103/PhysRevB.107.085106 |
| Indexed | SCI(E) |
| Appears in Collections: | 物理学院 |
