Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 56: Correlated Electrons: Quantum-Critical Phenomena – Theory
TT 56.3: Talk
Wednesday, March 18, 2015, 10:00–10:15, A 053
Interference of quantum critical excitations and soft diffusive modes in a disordered antiferromagnetic metal — •Philipp Weiß1, Boris Narozhny1, and Jörg Schmalian1,2 — 1Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, Karlsruhe, Germany — 2Institut für Festkörperphysik, Karlsruher Institut für Technologie, Karlsruhe, Germany
We study a two-dimensional metallic system close to an antiferromagnetic critical point within the framework of the spin-fermion model. The model describes fermionic quasiparticles interacting with bosonic collective spin modes close to the antiferromagnetic wave vector Q→. Since Q→ is a large momentum scale, in first order of the spin-fermion coupling, low-energy fermions are only coupled to spin fluctuations at "hot spots" of the Fermi surface which are connected by Q→. However, at second order a fermion at an arbitrary point of a generic Fermi surface can be scattered successively by two spin fluctuations via an intermediate high-energy state and, in total, suffer only a small momentum transfer. This gives rise to an interference of critical spin fluctuations and diffusive excitations of the disordered metal. Integrating out the fermionic high-energy modes above a certain low-energy cutoff, we derive an effective low-energy action which exhibits a local interaction vertex for low-energy fermions on the entire Fermi surface. This interaction is mediated by a composite propagator. Using a diagrammatic approach, we calculate the temperature-dependent interaction correction to dc-conductivity induced by the composite propagator in the presence of disorder and find a correction to residual resistivity.