Electronic structure and phonon instabilities in the vicinity of the structural transition and superconductivity of (Sr,Ca)$_3$Ir$_4$Sn$_{13}$

David A. Tompsett

doi:10.1103/PhysRevB.89.075117

paper

Electronic structure and phonon instabilities in the vicinity of the structural transition and superconductivity of (Sr,Ca) $_{3}$ Ir $_{4}$ Sn $_{13}$

arXiv:1401.6412 · doi:10.1103/PhysRevB.89.075117

Abstract

The nature of the lattice instability connected to the structural transition and superconductivity of (Sr,Ca) $_{3}$ Ir $_{4}$ Sn $_{13}$ is not yet fully understood. In this work density functional theory (DFT) calculations of the phonon instabilities as a function of chemical and hydrostatic pressure show that the primary lattice instabilities in Sr $_{3}$ Ir $_{4}$ Sn $_{13}$ lie at phonon modes of wavevectors $q = (0.5, 0, 0)$ and $q = (0.5, 0.5, 0)$ . Following these modes by calculating the energy of supercells incorporating the mode distortion results in an energy advantage of -14.1 meV and -9.0 meV per formula unit respectively. However, the application of chemical pressure to form Ca $_{3}$ Ir $_{4}$ Sn $_{13}$ reduces the energetic advantage of these instabilities, which is completely removed by the application of a hydrostatic pressure of 35 kbar to Ca $_{3}$ Ir $_{4}$ Sn $_{13}$ . The evolution of these lattice instabilities is consistent with experimental phase diagram. The structural distortion associated with the mode at $q = (0.5, 0.5, 0)$ produces a distorted cell with the same space group symmetry as the experimentally refined low temperature structure. Furthermore, calculation of the deformation potential due to these modes quantitatively demonstrates a strong electron-phonon coupling. Therefore, these modes are likely to be implicated in the structural transition and superconductivity of this system.

7 pages, 7 figures

Electronic structure and phonon instabilities in the vicinity of the structural transition and superconductivity of (Sr,Ca) $_{3}$ Ir $_{4}$ Sn $_{13}$

Abstract

References in corpus (4)

Cited by in corpus (20)

Electronic structure and phonon instabilities in the vicinity of the structural transition and superconductivity of (Sr,Ca)3​Ir4​Sn13​

Abstract

References in corpus (4)

Cited by in corpus (20)

Electronic structure and phonon instabilities in the vicinity of the structural transition and superconductivity of (Sr,Ca) $_{3}$ Ir $_{4}$ Sn $_{13}$