Band structure effects on superconductivity in the weak-coupling Hubbard model

James K. Freericks, Douglas J. Scalapino

Weak-coupling expansions (conserving approximations) are carried out for the attractive Holstein and Hubbard models (on an infinite-dimensional hypercubic lattice) that include all band-structure and vertex correction effects. Quantum fluctuations are found to renormalize transition temperatures by factors of order unity, but may be incorporated into the superconducting channel of Migdal-Eliashberg theory by renormalizing the phonon frequency and the interaction strength.

K. P. Jain, R. Ramakumar, C. C. Chancey

Masahisa Koga, Akihisa Koga

Sebastian Wolf, Thomas L. Schmidt, Stephan Rachel

In superconducting phases, repulsive interactions between the electrons usually lead to higher-angular momentum Cooper pairing. Here, the authors employ the weak-coupling renormalization group approach to study unconventional superconducting phases emerging in the extended, repulsive Hubbard model on paradigmatic two-dimensional lattices. Among their findings are extended regions of chiral topological superconductivity on the square, triangular, and honeycomb lattices. They provide detailed superconducting phase diagrams as well as the coupling strengths that quantify the corresponding critical temperatures depending on the band-structure parameters, band filling, and interaction parameters. The importance of the resolution and accuracy of the numerical integration for the method is discussed and a way to higher numerical efficiency provided.

V. A. Moskalenko, S. P. Kozhokaru, Nguyen Thi Que

Astrid Tranum Rømer, Thomas Maier, Andreas Kreisel +3 more

The authors present a comprehensive study of superconducting pairing in the one-band Hubbard model. By comparing different theoretical techniques, the paper shows that the hierarchy of pairing instabilities evolves smoothly from weak- to strong coupling. Additionally, the doping-dependence of the leading superconducting instability is mapped out, and found to be in agreement with previous theoretical studies of the one-band Hubbard model.