Role of vertex corrections in the spin-fluctuation–mediated pairing mechanism

¹ Institut für Theoretische Physik und Astrophysik, Universität Würzburg am Hubland, 97074 Würzburg, Germany
² Department of Physics, Hubei University - Wuhan 430062, PRC
³ Institut für Theoretische Physik, Computational Physics, Technische Universität Graz Petersgasse 16, A-8010 Graz, Austria

Received: 17 May 2005
Accepted: 15 July 2005

Abstract

We study numerically and partly diagrammatically the renormalization of the electron-spin interaction or vertex in a two-dimensional one-band Hubbard model with spin-fluctuation momentum transfer . We find that the renormalized electron-spin vertex decreases quite generally with decreasing temperature at all doping densities. As a combination of two concurring effects, i.e. the decrease of the vertex and the increase of the spin susceptibility, the effective pairing interaction increases with lowering temperature in the intermediate-correlation regime, but flattens off in the strong-correlation regime. Our findings indicate that in the high- cuprates the pairing mediated by antiferromagnetic spin fluctuations is substantially reduced due to vertex corrections.