Regensburg 2016 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 80: Correlated Electrons: (General) Theory 2
TT 80.5: Vortrag
Donnerstag, 10. März 2016, 17:15–17:30, H18
Ground state phase diagram of the repulsive fermionic t-t′ Hubbard model on the square lattice from weak-coupling — •Fedor Simkovic1, Xuan-Wen Liu2, Youjin Deng2, and Evgeny Kozik1 — 1King’s College London, Strand, London WC2R 2LS, UK — 2University of Science and Technology of China, Hefei, Anhui 230026, China
We obtain a complete and exact in the weak-coupling limit (U → 0) ground state phase diagram of the repulsive fermionic Hubbard model on the square lattice for filling factors 0 ≤ n ≤ 2 and next nearest neighbour hopping amplitudes 0 ≤ t′ ≤ 0.5. Phases are distinguished by the symmetry and the number of nodes of the superfluid order parameter. The phase diagram is richer than may be expected and typically features states with a high —higher than that of the fundamental mode of the corresponding irreducible representation— number of nodes. The effective coupling strength in the Cooper channel λ, which determines the critical temperature Tc of the superfluid transition, is calculated in the whole parameter space and regions with high values of λ are identified. It is shown that besides the expected increase of λ near the Van Hove singularity line, joining the ferromagnetic and antiferromagnetic points, another region with high values of λ can be found at quarter filling and t′=0.5 due to the presence of a line of nesting at t′ ≥ 0.5. The results can serve as benchmarks for controlled non-perturbative methods and guide the ongoing search for high-Tc superconductivity in the Hubbard model.