Scaling and commensurate-incommensurate crossover for the d = 2, z = 2 quantum critical point of itinerant antiferromagnetsS. Roy1 and A.-M. S. Tremblay1, 2
1 Département de Physique and Regroupement Québécois sur les Matériaux de Pointe, Université de Sherbrooke Sherbrooke, Québec, J1K 2R1, Canada
2 Institut Canadien de Recherches Avancées, Université de Sherbrooke - Sherbrooke, Québec, J1K 2R1, Canada
received 10 July 2008; accepted in final form 2 October 2008; published November 2008
published online 31 October 2008
Quantum critical points exist at zero temperature, yet, experimentally their influence seems to extend over a large part of the phase diagram of systems such as heavy-fermion compounds and high-temperature superconductors. Theoretically, however, it is generally not known over what range of parameters the physics is governed by the quantum critical point. We answer this question for the spin-density wave to Fermi-liquid quantum critical point in the two-dimensional Hubbard model. This problem is in the d = 2, z = 2 universality class. We use the two-particle self-consistent approach, which is accurate from weak to intermediate coupling, and whose critical behavior is the same as for the self-consistent-renormalized approach of Moriya. Despite the presence of logarithmic corrections, numerical results demonstrate that quantum critical scaling for the static magnetic susceptibility can extend up to very high temperatures but that the commensurate to incommensurate crossover leads to deviations to scaling.
71.10.Hf - Non-Fermi-liquid ground states, electron phase diagrams and phase transitions in model systems.
71.10.Fd - Lattice fermion models (Hubbard model, etc.).
73.43.Nq - Quantum phase transitions.
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