Sign Change in the Odd Parity Superconducting State of Iron-Based Superconductors
We discuss the sign change of superconducting order parameters in both real and reciprocal spaces in the odd parity state of iron-based superconductors proposed recently in\cite{huoddparity}. In the real space, the odd parity state can be viewed as a s-wave or d-wave state depending on the choice of locations. In a 2-Fe Brilliouin zone (BZ), sign change exists between two hole pockets and between two electron pockets. In a 1-Fe BZ which includes two 2-Fe BZs, the sign change is between two 2-Fe BZs, which leads to a d-wave type sign distribution on the electron pockets. However, there is no symmetry protected gapless node on the electron pockets. This sign change character consistently explains experimental results related to sign change properties measured on both iron-pnictides and iron-chalcogenides.