Low-Temperature Phase of the Cd$_2$Re$_2$O$_7$ Superconductor: Ab initio Phonon Calculations and Raman Scattering

Konrad J. Kapcia; Maureen Reedyk; Mojtaba Hajialamdari; Andrzej Ptok; Przemysław Piekarz; Fereidoon S. Razavi; Andrzej M. Oleś; Reinhard K. Kremer

doi:10.1103/PhysRevResearch.2.033108

paper

Low-Temperature Phase of the Cd $_{2}$ Re $_{2}$ O $_{7}$ Superconductor: Ab initio Phonon Calculations and Raman Scattering

arXiv:1911.11057 · doi:10.1103/PhysRevResearch.2.033108

Abstract

Using an {\it ab initio} approach, we report a phonon soft mode in the tetragonal structure described by the space group $I 4_{1} 22$ of the $1$ K $5 d$ superconductor Cd $_{2}$ Re $_{2}$ O $_{7}$ . It induces an orthorhombic distortion to a crystal structure described by the space group $F 222$ which hosts the superconducting state. This new phase has a lower total energy than the other known crystal structures of Cd $_{2}$ Re $_{2}$ O $_{7}$ . Comprehensive temperature dependent Raman scattering experiments on isotope enriched samples, $^{116}$ Cd $_{2}$ Re $_{2}^{18}$ O $_{7}$ , not only confirm the already known structural phase transitions but also allow us to identify a new characteristic temperature regime around $\sim 80$ K, below which the Raman spectra undergo remarkable changes with the development of several sharp modes and mode splitting. Together with the results of the \textit{ab initio} phonon calculations we take these observations as strong evidence for another phase transition to a novel low-temperature crystal structure of Cd $_{2}$ Re $_{2}$ O $_{7}$ .

7 pages, 8 figures

Low-Temperature Phase of the Cd $_{2}$ Re $_{2}$ O $_{7}$ Superconductor: Ab initio Phonon Calculations and Raman Scattering

Abstract

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Low-Temperature Phase of the Cd2​Re2​O7​ Superconductor: Ab initio Phonon Calculations and Raman Scattering

Abstract

References in corpus (10)

Cited by in corpus (4)

Low-Temperature Phase of the Cd $_{2}$ Re $_{2}$ O $_{7}$ Superconductor: Ab initio Phonon Calculations and Raman Scattering