Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 27: CE: Poster Session
TT 27.21: Poster
Mittwoch, 24. März 2010, 14:00–18:00, Poster D1
Luttinger-Ward functional approach in the Eliashberg framework : A systematic derivation of scaling for thermodynamics near a quantum critical point — •Adel Benlagra1, Ki-Seok Kim2, and Catherine Pépin3 — 1Institut für Theoretische Physik, Universität zu Köln, Germany — 2Institut de physique Théorique, CEA Saclay, France — 3Pacific Center for Theoretical Physics, POSTECH, Pohang, South Korea
The poster by Duc-Anh Le et. al. originally scheduled for TT 27.21 has been withdrawn and was replaced by this poster.
We used the Luttinger-Ward (LW) functional in the Eliashberg framework to derive scaling expressions for the free energy from a microscopic model for two models of quantum criticality : the standard theoretical framework called the Hertz-Moriya-Millis theory and the Kondo breakdown model, one possible scenario for heavy-fermion quantum transitions, for which the effective theory is given by a U(1) gauge theory.
The LW functional approach allows to take into account the fluctuation corrections in a systematic way. The Eliashberg framework allows to use the proper level of approximation to get, self-consistently, the correct scaling for thermodynamics near the quantum critical point. We have shown that, at the one loop level, the fermionic excitations give a Fermi Liquid contribution whereas the singular part of the free energy for both models is due to the collective bosonic excitations. In particular, the Kondo breakdown QCP is characterized by two length scales : one is the correlation length for hybridization fluctuations, and the other is that for gauge fluctuations, analogous to the penetration depth in superconductors.