The recent paper by V. G. Kogan and J. Schmalian [Phys. Rev. B 83, 054515 (2011)] argues that the widely used two-component Ginzburg-Landau (GL) models are not correct, and further concludes that in the regime which is described by a GL theory there could be no disparity in the coherence lengths of two superconducting components. This would in particular imply that [in contrast to $U\left(1\right)\times U\left(1\right)$ superconductors] there could be no “type-1.5” superconducting regime in $U\left(1\right)$ multiband systems for any finite interband coupling strength. We point out that these claims are incorrect and based on an erroneous scheme of reduction of a two-component GL theory.

• Received 18 May 2011

DOI:https://doi.org/10.1103/PhysRevB.86.016501