First-order structural transition and pressure-induced lattice/phonon anomalies in Sr2IrO4
| Autor: | F. M. Ardito, K. Samanta, E. Granado, N. M. Souza-Neto |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Physics
Superconductivity Strongly Correlated Electrons (cond-mat.str-el) Condensed matter physics Magnetic moment Phonon FOS: Physical sciences 02 engineering and technology Crystal structure 021001 nanoscience & nanotechnology 01 natural sciences Condensed Matter - Strongly Correlated Electrons Condensed Matter::Materials Science Tetragonal crystal system Condensed Matter::Superconductivity Lattice (order) 0103 physical sciences Condensed Matter::Strongly Correlated Electrons Cuprate 010306 general physics 0210 nano-technology Powder diffraction |
| Zdroj: | Physical Review B. 98 |
| ISSN: | 2469-9969 2469-9950 |
| Popis: | We investigate the crystal structure and lattice vibrations of Sr$_2$IrO$_4$ by a combined phonon Raman scattering and x-ray powder diffraction experiment under pressures up to $66$ GPa and room temperature. Density functional theory (DFT) and $ab$-initio lattice dynamics calculations were also carried out. A first-order structural phase transition associated with an $8$ % collapse of the $c$-axis is observed at high pressures, with phase coexistence being observed between $\sim 40$ and $55$ GPa. At lower pressures, lattice and phonon anomalies were observed, reflecting crossovers between isostructural competing states. A critical pressure of $P_1=17$ GPa is associated with: (i) a reduction of lattice volume compressibility and a change of behavior of the tetragonal $c/a$ ratio take place above $P_1$; (ii) a four-fold symmetry-breaking lattice strain associated with lattice disorder; (iii) disappearance of two Raman active modes (at $\sim 180$ and $\sim 260$ cm$^{-1}$); and (iv) development of an asymmetric Fano lineshape for the $\sim 390$ cm$^{-1}$ mode. DFT indicates that the phase above $P_1$ is most likely non-magnetic. Exploring the similarities between iridate and cuprate physics, we argue that these observations are consistent with the emergence of a rotational symmetry-breaking electronic instability at $P_1$, providing hints for the avoided metallization under pressure and supporting the hypothesis of possible competing orders that are detrimental to superconductivity in this family. Alternative scenarios for the transition at $P_1$ are also suggested and critically discussed. Additional phonon and lattice anomalies in the tetragonal phase are observed at $P_2=30$ and $P_3=40$ GPa, indicating further competing phases that are stabilized at high pressures. 10 pages, 10 figures + 4 Appendices |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|