2006/02/07 by Mona Berciu · 3 citations
Mathematics · Physics and Astronomy · #Diagram #Function (biology) #Mathematical physics #Mathematics #Physics #Physics of Superconductivity and Magnetism #Polaron #Propagator #Quantum and electron transport phenomena #Quantum chromodynamics #Quantum mechanics #Sum rule in quantum mechanics #Theoretical and Computational Physics #cond-mat.other
paper · pdf · doi:10.1103/physrevlett.97.036402
published as Phys. Rev. Lett. 97, 036402 (2006). · 4 pages, 3 figures
arxiv created 2006/02/07 · openalex publication_date 2006/07/19 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present a new, highly efficient yet accurate approximation for the Green's functions of dressed particles, using the Holstein polaron as an example. Instead of summing a subclass of self-energy diagrams (e.g., the noncrossed ones, in the self-consistent Born approximation), we sum all the diagrams, but with each diagram averaged over its free propagators' momenta. The resulting Green's function satisfies exactly the first six spectral weight sum rules. All higher sum rules are satisfied with great accuracy, becoming asymptotically exact for coupling both much larger and much smaller than the free particle bandwidth. Possible generalizations to other models are also discussed.