https://doi.org/10.65770/UVWB1716
ABSTRACT
It has been found that a thin, high dielectric constant substrate can suppress superconductivity in twisted bilayer graphene . The high dielectric constant of substrate effectively screens and weakens the strong electronic interactions required for Cooper pair formation in , thereby suggesting that the superconductivity in this system is driven by unconventional electronic interactions rather than the well-known phonon interactions. Using some of these ideas, the superconducting properties and parameters of bilayer graphene , twisted bilayer graphene, and magic-angle-twisted-bilayer-graphene , separated by a thin dielectric of thickness , are investigated under the assumption that the thickness of the upper and lower graphene layers are much greater than , less than or equal to . Physical parameters such as heat capacity and transition temperatures were calculated for different values of energy gap and geometric parameters . It was found that the heat capacity decreases monotonically with increasing temperature for both and , indicating that thermal excitations are progressively suppressed as the energy gap increases, while in the case of a local enhancement that indicate a thermal crossover region was noted at T=250K. The calculated transition temperatures were noted to increase linearly with the energy gap for all the three models considered. The derived model consistently predicted transition temperatures that lie between those of magic-angle twisted bilayer graphene (MATBG) and conventional bilayer graphene superconductors with a dielectric spacer. At the highest investigated energy gap , the derived model predicts compared with for MATBG model and for the dielectric mediated BG model. These results indicate that the derived model captures the essential superconducting behavior of bilayer graphene while predicting a significant enhancement in superconducting performance relative to MATBG systems.
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