Rational material design of mixed-valent high-T_c superconductors

We design, from first-principles calculations, a novel family of thallium halide-based compounds as candidates for new high-temperature superconductors, whose superconductivity is mediated by the recently proposed mechanism of non-local correlation-enhanced strong electron-phonon coupling. Two prototype compounds namely CsTlF₃ and CsTlCl₃ are studied with various hole doping levels and volumes. The critical superconducting temperatures (T_c's) are predicted to be about 30 K and 20 K with ∼0.35/f.u. hole doping and require only modest pressures (∼10 and ∼2 GPa), respectively. Our procedure of designing this class of superconductors is quite general and can be used to search for other "other high-temperature superconductors".