EPL, 88 (2009) 17004
DOI: 10.1209/0295-5075/88/17004

Collective modes and emergent symmetry of superconductivity and magnetism in the iron pnictides

D. Podolsky^{1, 2}, H.-Y. Kee¹ and Y. B. Kim<sup>1

1</sup>   Department of Physics, University of Toronto - Toronto, Ontario M5S 1A7, Canada
²   Physics Department, Technion - Haifa 32000, Israel

received 11 May 2009; accepted in final form 16 September 2009; published October 2009
published online 16 October 2009

Abstract
We consider the two-pocket model of the iron pnictides with generic interactions, and show that the low-energy effective theory of this model belongs to a wide class of Hamiltonians with enhanced symmetry. We consider the effect of symmetry breaking perturbations around such systems and explore the physical consequences. Our analysis reveals that the presence of the spin density wave with ordering wave vector (, 0) necessarily implies the existence of odd-sign s-wave superconductivity. We predict a spin-triplet resonance at the wave vector (, 0) whose frequency depends linearly on applied field and is independent of temperature. We also discuss the possible presence of a novel orbital density wave state as a close competing order encompassed by the emergent SO(6) symmetry.

PACS
74.20.De - Phenomenological theories (two-fluid, Ginzburg-Landau, etc.).
74.25.Ha - Magnetic properties.

© EPLA 2009