Alexander Fetter and John Dirk Walecka’s Quantum Theory of Many-Particle Systems stands as one of the most influential textbooks in the history of modern physics. Since its original publication in 1971, it has served as the definitive gateway for graduate students and researchers into the complex world of many-body physics. By providing a rigorous foundation in second quantization and Green’s functions, the text bridged the gap between basic quantum mechanics and the sophisticated field-theoretic methods used in nuclear, atomic, and condensed matter physics.
The discovery of correlated insulators and superconductivity in "magic-angle" graphene requires sophisticated many-body treatments. The Green's function formalism of FW is the starting point for understanding how flat bands enhance electron-electron interactions. Alexander Fetter and John Dirk Walecka’s Quantum Theory
Buy the Dover paperback or e-book. It costs less than a pizza and a beer. In return, you get a "new" PDF that is searchable, legal, and will serve you from your first day of graduate school to your last day as a senior researcher. The quantum many-body problem is still unsolved for most real materials; the tools Fetter and Walecka gave us remain the sharpest we have. It costs less than a pizza and a beer