Berezinskii-Kosterlitz-Thouless transition in a binary Bose mixture with Rabi coupling

We discuss the Berezinskii-Kosterlitz-Thouless transition in a 2D binary Bose mixture with Rabi coupling under balanced densities. Adopting the Nelson-Kosterlitz renormalization group approach, we clarify the dependence of the Berezinskii-Kosterlitz-Thouless transition temperature on the Rabi coupling and the inter-component coupling. In particular, we find an amplification of the transition temperature with respect to the one in the single-component case for finite values of Rabi coupling and small intra-component couplings. We also evaluate the first sound and second sound velocity, which exhibits suppression of quasicrossing of the two sound modes with a finite Rabi coupling in the low-temperature regime.