Superconductivity in predicted two dimensional XB6 (X = Ga, In)

Abstract

Recently, two-dimensional (2D) rect-AlB₆ [B. Song, Y. Zhou, H.-M. Yang, J.-H. Liao, L.-M. Yang, X.-B. Yang and E. Ganz, J. Am. Chem. Soc., 2019, 141, 3630–3640] has been reported to be an excellent system, exhibiting intrinsic superconductivity. Here, on the basis of the CALYPSO structure prediction method and first-principles calculations, we predict two novel systems of 2D XB₆ (rect- and hex-XB₆) (X = Ga, In), verify their thermal stability and calculate their mechanical properties. Then, we study their bonding nature, electron and phonon properties, and electron–phonon coupling (EPC). The results show that rect-, hex-GaB₆, rect- and hex-InB₆ are intrinsic phonon-mediated superconductors with a superconducting transition temperature (T_c) of 1.67, 14.02, 7.77 and 4.83 K, respectively. Furthermore, we study the influence of strain on these intrinsic superconductors. Their T_c can be modulated to some extent, especially for hex-InB₆, the T_c of which can be enhanced to 19.23 K under the compressive strain of 2%. According to our calculations, they may be prepared by growing on suitable substrates, such as Cu(100) and Pt(111). Our findings may broaden the configurations of 2D superconducting materials and will stimulate more efforts in this field.