Time-Reversal Symmetry Breaking Superconductivity in the Coexistence Phase with Magnetism in Fe Pnictides

Alberto Hinojosa, Rafael M. Fernandes, and Andrey V. Chubukov

Phys. Rev. Lett. 113, 167001 – Published 13 October 2014

Abstract

We argue that superconductivity in the coexistence region with spin-density-wave (SDW) order in weakly doped Fe pnictides erdiffers qualitatively from the ordinary $s^{+ -}$ state outside the coexistence region as it develops an additional gap component which is a mixture of intrapocket singlet ( $s^{+ +}$ ) and interpocket spin-triplet pairings (the $t$ state). The coupling constant for the $t$ channel is proportional to the SDW order and involves interactions that do not contribute to superconductivity outside of the SDW region. We argue that the $s^{+ -}$ - and $t$ -type superconducting orders coexist at low temperatures, and the relative phase between the two is, in general, different from 0 or $π$ , manifesting explicitly the breaking of the time-reversal symmetry promoted by long-range SDW order. We argue that time reversal may get broken even before true superconductivity develops.

Received 27 May 2014

DOI:https://doi.org/10.1103/PhysRevLett.113.167001

Authors & Affiliations

Alberto Hinojosa¹, Rafael M. Fernandes², and Andrey V. Chubukov¹

¹Department of Physics, University of Wisconsin, Madison, Wisconsin 53706, USA
²School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA