  Spin-isospin transitions in nuclei away from the valley of stability are
essential for the description of astrophysically relevant weak interaction
processes. While they remain mainly beyond the reach of experiment, theoretical
modeling provides important insight into their properties. In order to describe
the spin-isospin response,vcthe proton-neutron relativistic quasiparticle
random phase approximation (PN-RQRPA) is formulated using the relativistic
density-dependent point coupling interaction, and separable pairing interaction
in both the $T=1$ and $T=0$ pairing channels. By implementing recently
established DD-PCX interaction with improved isovector properties relevant for
the description of nuclei with neutron-to-proton number asymmetry, the isobaric
analog resonances (IAR) and Gamow-Teller resonances (GTR) have been
investigated. In contrast to other models that usually underestimate the IAR
excitation energies in Sn isotope chain, the present model accurately
reproduces the experimental data, while the GTR properties depend on the
isoscalar pairing interaction strength. This framework provides not only an
improved description of the spin-isospin response in nuclei, but it also allows
future large scale calculations of charge-exchange excitations and weak
interaction processes in stellar environment.
