Effective projection theory in a correlated electron system

• Published in: Journal of physics. Condensed matter Vol. 22; no. 48; p. 485604
• Main Authors: Yi, Juyeon, Kim, Seongjin, Um, Jaegon, Hwang, Sun-Yong, Go, Ara, Jeon, Gun Sang
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 08.12.2010; Institute of Physics
• Subjects: Atomic and molecular physics; Electron correlation calculations for atoms and molecules; Electronic structure of atoms, molecules and their ions: theory; Exact sciences and technology; Physics; Diagonalization; Ground states; Weak interactions; Calcium nitride; Strong interactions; Wave functions; Anderson model; Equations of motion; Green's function methods; Green function
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/22/48/485604

We propose an efficient method for nonperturbative calculation of Green's function in a correlated electron system. The key idea of the method is to project out irrelevant operators having zero norm in the ground state, which we refer to as effective projection theory. We apply the method to a mesoscopic Anderson model and show that for a given wavefunction ansatz, equations of motion can be closed only by relevant operators, allowing easy calculation of the zero-temperature Green's function. It turns out that the resulting Green's functions reproduce exact limits of both weak and strong interactions. The accuracy is also verified for small systems by comparison with exact diagonalization results, revealing that effective projection theory captures the essential correlated features in the entire regime of interactions.