Pseudospin-phonon pretransitional dynamics in lead halide hybrid perovskites

Abstract

The low frequency lattice vibrations and relaxations are investigated in single crystals of the four 3D hybrid organolead perovskites, MAPbBr${}_3$, FAPbBr${}_3$, MAPbI${}_3$, and $\alpha$-FAPbI${}_3$, at the Brillouin zone center using Raman and Brillouin scattering and at the zone boundary using inelastic neutron scattering. The temperature dependence of the PbX${}_6$ lattice modes in the four compounds can be renormalized into universal curves, highlighting a common vibrational dynamics at the cubic to tetragonal transition. In particular, no soft vibration is observed excluding a displacive-like transitional dynamics. The reorientational (pseudospin) motions of the molecular cations exhibit a seemingly order-disorder character recalling that of plastic crystals, but attributed to a secondary order-parameter. At ultra-low frequency, a quasi-elastic component evidenced by Brillouin scattering and associated to the unresolved central peak observed in neutron scattering, is attributed to center of mass anharmonic motions and rattling of the molecular cations in the perovskite cavities. Its partially unexpressed critical behavior at the transition points toward the general importance of defects in HOPs preventing the net divergence of order parameter correlations at the critical temperatures.

arXiv comment10 figures, supplemental file upon request, accepted in PRB

References in corpus (15)

• Local polar fluctuations in lead halide perovskite crystals
• Lattice dynamics and vibrational spectra of the orthorhombic, tetragonal and cubic phases of methylammonium lead iodide
• Dynamic disorder, phonon lifetimes, and the assignment of modes to the vibrational spectra of methylammonium lead halide perovskites
• Towards predictive many-body calculations of phonon-limited carrier mobilities in semiconductors
• Direct Observation of Dynamic Symmetry Breaking above Room Temperature in Methylammonium Lead Iodide Perovskite
• Rotational Dynamics of Organic Cations in CH3NH3PbI3 Perovskite
• Elastic softness of hybrid lead halide perovskites
• From soft harmonic phonons to fast relaxational dynamics in CH${}_3$NH${}_3$PbBr${}_3$
• Carrier Lifetimes and Polaronic Mass Enhancement in the Hybrid Halide Perovskite CH${}_3$NH${}_3$PbI${}_3$ from Multiphonon Fröhlich Coupling
• Anharmonic stabilization and band gap renormalization in the perovskite CsSnI${}_3$
• Direct evidence of weakly dispersed and strongly anharmonic optical phonons in hybrid perovskites
• Lattice dynamics and the nature of structural transitions in organolead halide perovskites
• Decoupled molecular and inorganic framework dynamics in CH${}_3$NH${}_3$PbCl${}_3$
• On the question of dynamic domains and critical scattering in cubic methylammonium lead triiodide
• Temporally-decoherent and spatially-coherent vibrations in metal halide perovskite

Cited by in corpus (4)

• Anharmonic electron-phonon coupling in ultrasoft and locally disordered perovskites
• Dynamic Nanodomains Dictate Macroscopic Properties in Lead Halide Perovskites
• Untangling the Raman spectrum of cubic and tetragonal BaZrO${}_3$
• Guest-induced phase transition leads to polarization enhancement in MHyPbCl3