Superconductivity in Monolayer Carbon Allotropes with High Thermal Stability.

Xia, Kang; Yu, Xiaolong; Ding, Chi; Lu, Qing; Zhang, Zhongwei; Sun, Jian · Nano Lett · 2024

basic_science · Level V

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Abstract

Intrinsic superconductivity is rarely discovered in <i>sp</i><sup>2</sup>-hybridized monolayer carbon allotropes. Here we design a carbon monolayer configured of pentagon, heptagon, and hexagon rings with <i>p</i><i>2</i> plane group symmetry. Full-<i>sp</i><sup>2</sup> hybridization is proposed to favor thermal metastability on a low Gibbs free energy. The extremely small thermal expansion coefficient is predicted to the turn negative value to positive with elevating temperature. Carbon polygon structures remain intact at a high thermal temperature of 3,000 K. The high specific surface area is found to approach 2,700 m<sup>2</sup>/g, with O<sub>2</sub>-adsorption being advantageous over pristine graphene. We reveal electronic Fermi surfaces mediated by phonon modes of carbon out-of-plane vibrations. By calculating the Eliashberg equation, we evaluate intrinsic superconductivity with a large electron-phonon coupling coefficient. The superconducting transition temperature is estimated to reach 20 K under a high logarithmic average frequency. These first-principles calculations shall stimulate experimentalists' interest in exploring low-dimensional carbon superconductors with gas sensitivity.