Thermodynamic Properties of Superconducting State in Intercalated Bilayer Graphene

K.M. Skoczylasa, A.P. Durajskib, R. Szczęśniakb aInstitute of Physics, Jan Długosz University in Częstochowa, al. Armii Krajowej 13/15, 42-200 Częstochowa, Poland bInstitute of Physics, Częstochowa University of Technology, al. Armii Krajowej 19, 42-200 Częstochowa, Poland

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To this day, no evidence of superconducting state in monolayer graphene has been observed. However, the easily manageable two dimensional structure of graphene through almost freely doping allows to change the properties of the structure. In fact, the resistivity drop has been detected in graphene bilayer tilted by small angle and Ca intercalated bilayer. This work comprises investigation on the thermodynamic properties of the superconducting state in intercalated graphene bilayer system C6XC6 (where X is either K, Ca, Rb or Sr). Eliashberg theory of superconductivity allowed to compute on the quantitative level the thermodynamic quantities, including the transition temperature, free energy, entropy and specific heat difference between the superconducting and the normal state. Highest critical temperature was obtained for calcium intercalated bilayer (Tc=14.56 K), while the insertion of potassium and strontium lead to similar temperature values of 8.67 K and 8.74 K. In addition, the calculated BCS ratios: RΔ, RC, and RH deviate significantly from the constant, theoretical values.

DOI:10.12693/APhysPolA.137.776 topics: Superconductivity, graphene, bilayer