Maximal superconductivity in proximity to the charge density wave quantum critical point in CuxTiSe2

Article

关键词: TRANSITION-TEMPERATURE;    SUPERLATTICE FORMATION;    LATTICE-DYNAMICS;   

DOI  :  10.1103/PhysRevB.104.184506

来源: SCIE

【 摘 要 】

Superconductivity emerges in 1T-TiSe2 when its charge density wave (CDW) order is suppressed by Cu intercalation or pressure. Since the CDW state is thought to be an excitonic insulator, an interesting question is whether the superconductivity is also mediated by excitonic fluctuations. We investigated this question as to the nature of doping induced superconductivity in CuxTiSe2 by asking about its consistency with the phonon mediated pairing. We employed the ab initio density functional theory and density functional perturbation theory to compute the electron-phonon coupling Eliashberg function from which to calculate the superconducting (SC) critical temperature T-c. The calculated T-c as a function of the doping concentration x exhibits a dome shape with the maximum T-c of 2-6 K at x approximate to 0.05 for the Coulomb pseudopotential 0 <= mu* <= 0.1. The maximal T-c was found to be pinned to the quantum critical point where the CDW is completely suppressed and the corresponding phonon mode becomes soft. Underlying physics is that the reduced phonon frequency enhances the electron phonon coupling constant lambda, which overcompensates the frequency decrease to produce a net increase of T-c. The doping induced superconductivity in CuxTiSe2 seems to be consistent with the phonon-mediated pairing. A comparative discussion was made with the pressure induced superconductivity in TiSe2.

【 授权许可】

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