23,090 research outputs found

    Rational material design of mixed-valent high Tc_c superconductors

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    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_3 and CsTlCl3_3 are studied with various hole doping levels and volumes. The critical superconducting temperature Tc_c are predicted to be about 30 K and 20 K with ∼\sim0.35/f.u. hole doping and require only modest pressures (∼\sim10 and ∼\sim2 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".Comment: 6- ages, EPL 101, 27002 (2013

    Correlation-enhanced electron-phonon coupling: Applications of GW and screened hybrid functional to bismuthates, chloronitrides, and other high Tc superconductors

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    We show that the electron-phonon coupling (EPC) in many materials can be significantly underestimated by the standard density functional theory (DFT) in the local density approximation (LDA) due to large non-local correlation effects. We present a simple yet efficient methodology to evaluate the realistic EPC going beyond LDA by using more advanced and accurate GW and screened hybrid functional DFT approaches. The corrections we propose explain the extraordinarily high superconducting temperatures that are observed in two distinct classes of compounds-the bismuthates and the transition metal chloronitrides, thus solving a thirty-year-old puzzle. Our work calls for the critically reevaluation of the EPC of certain phonon modes in many other materials such as cuprates and iron-based superconductors. The proposed methodology can be used to design new correlation-enhanced high temperature superconductors and other functional materials involving electron-phonon interaction.Comment: Substantilly extended version of the previous manuscript, 19 pages, 10 figures, accepted for publication in Phys. Rev.
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