Computational design of a new layered superconductor LaOTlF

A new layered compound LaOTlF 2 is designed and investigated using first-principles calculations in this work. The parent compound is an insulator with an indirect band gap of 3.88 eV. Electron-doping of the parent compound makes the material metallic. In the meantime, several lattice vibrational modes couple strongly to the conduction band, leading to a large electron-phonon coupling constant and conventional superconductivity. The highest superconducting transition temperature T c is predicted to be approximately 8.6 K with λ about 1.25 in the optimally doped LaO 0.95 F 0.05 TlF 2 , where λ is calculated using the Wannier interpolation technique. Two new layered superconductor families, La(O,F)TlF 2 and La(O,F)TlCl 2 , are designed and investigated using first-principles calculations which predict that the highest superconducting temperatures are ∼8.6 K and 8.1 K at 13% and 15% F doping, respectively.