In the paper Symmetries and conservation laws in non-Hermitian field theories by Jean Alexandre, Peter Millington, and Dries Seynaeve, Phys. Rev. D 96, 065027 the authors use this Lagrangian:
$$ L = \partial_\nu \phi_1^* \partial^\nu \phi_1 + \partial_\nu \phi_2^* \partial^\nu \phi_2 - m_1^2 \phi_1^* \phi_1 - m_2^2 \phi_2^* \phi_2 - \mu^2 (\phi_1^* \phi_2 - \phi_2^* \phi_1).$$
But they do not explain its origin. I can't find anywhere from where this Lagrangian has come and where in physics it's being used. Please tell about its origin and use or give any references from where I can find about it.