Prediction of novel layered indium halide superconductors

We design two new layered indium halide compounds LaOInF₂ and LaOInCl₂ by means of first-principles calculations and evolutionary crystal structure prediction. We find both compounds crystallize in a tetragonal structure with P4/nmm space group and have indirect band gaps of 2.58 eV and 3.21 eV, respectively. By substituting O with F, both of them become metallic and superconducting at low temperature. The F-doping leads to strong electron–phonon coupling in the low-energy acoustic phonon modes which is mainly responsible for the induced superconductivity. The total electron–phonon coupling strength are 1.86 and 1.48, while the superconducting transition temperature (T_c) are about 7.2 K and 6.5 K with 10% and 5% F doping for LaOInF₂ and LaOInCl₂, respectively.