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TT: Fachverband Tiefe Temperaturen

TT 79: Correlated Electrons - Poster Session

TT 79.32: Poster

Mittwoch, 2. April 2014, 15:00–19:00, P2

Superconducting gap at a ferromagnetic quantum critical point — •Matthias Einenkel¹, Hendrik Meier², Catherine Pépin³, and Konstantin B. Efetov¹ — ¹Institut für Theoretische Physik III, Ruhr-Universität Bochum, 44780 Bochum, Germany — ²Department of Physics, Yale University, New Haven, CT 06520, USA — ³IPhT, CEA-Saclay, L'Orme des Merisiers, 91191 Gif-sur-Yvette, France

We discuss the quantum critical behaviour of a two-dimensional quantum ferromagnet in the context of the spin-fermion model. In this system fermions interact with critical bosonic excitations. We investigate the system by first performing a mean-field analysis, and show that close to the quantum critical point a superconducting gap appears which has spin triplet symmetry. Further, we calculate the action of the Goldstone modes associated with this symmetry breaking and derive a non-linear sigma model. These fluctuations turn out to be not suppressed by any small parameter and therefore eventually destroy the order. This reveals the failure of the large N expansion which was reported by previous works.