Point-contact spectroscopy of electron-phonon interactions and anisotropy of superconducting energy gaps in $2H-NbS{{e}_{2}}$

The superconducting state of $2H-NbS{{e}_{2}}$ was studied using point contacts for two main orientations of the contact axis relative to the principal crystallographic orientations: along the $c$-axis and in the $ab$ plane. For contacts oriented in the $ab$ plane, dependencies proportional to the electron-phonon interaction function were obtained, which agree perfectly with the theoretical calculation. It was found that the features on the experimental curves associated with the electron-phonon interaction extend to energies twice the cutoff energy of the phonon spectrum and have an amplitude of the same order of magnitude throughout the entire energy range. It has been theoretically demonstrated that the features at energies exceeding the boundaries of the phonon density of states are caused by two-phonon scattering processes of non-equilibrium phonons on Andreev electrons. A criterion for the undisturbed nature of the crystal lattice in the region where gap features form has been found. Using $2H-NbS{{e}_{2}}-Cu$ heterocontacts in the superconducting state, a study of energy gaps was conducted for two orientations of the $NbS{e_2}$ crystal: along the $c$-axis and in the $ab$ plane. It was found that the superconducting energy gaps are anisotropic; specifically, three gaps were identified in the $ab$ plane, whereas only two were observed in the $c$ direction.