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Low-Temperature Phase of the Cd$_2$Re$_2$O$_7$ Superconductor: Ab initio Phonon Calculations and Raman Scattering
- Source :
- Physical Review Research 2, 033108 (2020)
- Publication Year :
- 2019
-
Abstract
- Using an {\it ab initio} approach, we report a phonon soft mode in the tetragonal structure described by the space group $I4_{1}22$ of the $1$ K $5d$ superconductor Cd$_2$Re$_2$O$_7$. It induces an orthorhombic distortion to a crystal structure described by the space group $F222$ 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$_7$.<br />Comment: 7 pages, 8 figures
- Subjects :
- Condensed Matter - Superconductivity
Condensed Matter - Materials Science
Subjects
Details
- Database :
- arXiv
- Journal :
- Physical Review Research 2, 033108 (2020)
- Publication Type :
- Report
- Accession number :
- edsarx.1911.11057
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1103/PhysRevResearch.2.033108