Superconducting properties of a boson-exchange model of doped graphene

Анотація

We study the superconducting properties of a doped one-layer graphene by using a model in which the interparticle attraction is caused by a boson (phonon-like) excitations. We study the dependencies of the superconducting gap D and the mean-field critical temperature T_c^MF on the carrier density, attraction strength and the characteristic (Debye) bosonic frequency. In addition, we study the temperature-carrier density phase diagram of the model by taking into account the thermal fluctuations of the order parameter. We show that the fluctuations result in a significant suppression of T_c^MF, such that the real (Berezinskii– Kosterlitz–Thouless) critical temperature T_c is much lower than T_c^MF. The region T_c < T < T_c^MF is characterized by a finite density of states at the Fermi level (the pseudogap phase). We show that the width of the temperature interval of the pseudogap phase strongly depends on the model parameters—carrier concentration, attraction amplitude, and boson frequency.