Enhancement mechanism of electron–phonon coupling in XB3 (X = K and Rb) compounds with Kagome lattice

Abstract

Kagome superconductors are a recent hot topic in superconductivity, while most studies focus on ternary systems. This study investigated the Kagome lattice and other structure properties of binary XB₃ (X = K and Rb) compounds in the pressure range of 0–30 GPa using crystal structure prediction and first-principles calculations. The crystal properties and bonding characteristics of the Cmmm, I4/mmm, P6/mmm, and P6₃/mmc phases were analyzed. The electronic band and density of states revealed that the I4/mmm and P6₃/mmc phases exhibit a semiconducting behavior. In contrast, the P6/mmm phase displays a Kagome lattice, and metallic and low Vickers hardness behaviors. Furthermore, superconducting critical temperatures (T_c) of the P6/mmm phase have been calculated, with T_c values of 26.7 and 28.2 K for KB₃ and RbB₃ at 0 GPa, respectively. The enhancement mechanism of electron–phonon coupling is discussed in detail, thereby revealing the intrinsic connection between the Kagome lattice and superconductivity in XB₃_P6/mmm compounds. Our results indicate that the XB₃ compounds demonstrate outstanding properties, including semiconducting behavior and the Kagome lattice, providing valuable theoretical insights for the exploration of new semiconductors and superconductors.