Theoretical Prediction of Phonon-Mediated Superconductivity in 2D ZrBx (x = 4 and 6) Monolayers

Two-dimensional (2D) superconductors have been studied extensively because of their potential applications in nanosuperconducting devices. Based on the crystal structure prediction method, we identified an energetically and dynamically stable monolayer structure for 2D ZrB6. Through first-principles calculations and comparison with the 2D ZrB4 monolayer, we discovered that both are intrinsic phonon-mediated superconductors, and ZrB6 has a higher superconducting transition temperature of 15.79 K, while ZrB4 has only 1.98 K. Further investigation revealed that the discrepancy is due to the varied coordinating environment. The structure of the pure plane formed by the larger coordination number inhibits the in-plane vibration of the Zr and B atoms in the ZrB4 monolayer. These findings will aid in the design and research of 2D high-temperature superconductors.