Study of the superconducting phase in silicene under biaxial tensile strain

• Thermodynamic properties of the superconducting silicene.
• The strong-coupling Eliashberg formalism.
• The high critical temperature.
• The non-BCS value of the ratio of the energy gap to the critical temperature.
• The large electron effective mass.

The electron-doped silicene under the influence of the biaxial tensile strain is predicted to be the phonon-mediated superconductor. By using the Eliashberg formalism, we investigate the thermodynamic properties of the superconducting silicene in the case when the tension is 5% and the electron doping equals 3.5×1014cm−2. Under such conditions, silicene monolayer is expected to exhibit the highest superconducting transition temperature (TC). In particular, based on the electron–phonon spectral function and assuming a wide range of the Coulomb pseudopotential values (μ⋆∈〈0.1,0.3〉μ⋆∈〈0.1,0.3〉) it is stated that the superconducting transition temperature decreases from 18.7 K to 11.6 K. Similar behavior is observed in the case of the zeroth temperature superconducting energy gap at the Fermi level: 2Δ(0)∈〈6.68,3.88〉2Δ(0)∈〈6.68,3.88〉 meV. Other thermodynamic parameters differ from the predictions of the Bardeen–Cooper–Schrieffer theory. In particular, the ratio of the energy gap to the critical temperature changes in the range from 4.14 to 3.87. The ratio of the specific heat jump to the specific heat in the normal state takes the values from 2.19 to 2.05, and the ratio of the critical temperature and specific heat in the normal state to the thermodynamic critical field increases from 0.143 to 0.155. It is also determined that the maximum value of the electron effective mass equals 2.11 of the electron band mass.