Abstract
Halide perovskite (HP) semiconductors exhibit unique strong coupling between the electronic and structural dynamics. We use Raman polarization-orientation (PO) measurements and ab initio molecular dynamics (AIMD) to investigate the origin and temperature evolution of the strong structural anharmonicity throughout the tetragonal phase of CH3NH3PbI3. Raman PO measurements reveal a soft modelike spectral feature. This mode shows an unusual continuous increase in damping with temperature which is indicative of an anharmonic potential surface. The analysis of AIMD trajectories identifies two major sources of anharmonicity: the orientational unlocking of the [CH3NH3](+) ions and large-amplitude octahedral tilting that continuously increases with temperature. Our work suggests that the standard phonon picture cannot describe the structural dynamics of tetragonal CH3NH3PbI3.
| Original language | English |
|---|---|
| Article number | 092401 |
| Number of pages | 6 |
| Journal | Physical Review Materials |
| Volume | 4 |
| Issue number | 9 |
| DOIs | |
| Publication status | Published - 1 Sept 2020 |
Funding
The authors would like to thank Dr. Tsachi Livneh (NRC) for fruitful discussions, Dr. Ishay Feldman (WIS) for performing x-ray diffraction measurements, and Dr. Lior Segev (WIS) for developing the Raman software. R.S. acknowledges FGS-WIS for financial support. O.Y. acknowledges funding from ISF (1861/17), BSF (Grant No. 2016650), ERC (850041-ANHARMONIC), Benoziyo Endowment Fund, Ilse Katz Institute, Henry Chanoch Krenter Institute, Soref New Scientists Start up Fund, Carolito Stiftung, Abraham and Sonia Rochlin Foundation, E. A. Drake and R. Drake, and the Perlman Family. Z.D. and L.G. acknowledge support from the U.S. National Science Foundation, under Grant No. DMR-1719353. J.Z. acknowledges support from a VIEST Fellowship at the University of Pennsylvania. A.M.R. acknowledges support from the Department of Energy, Office of Science, Office of Basic Energy Sciences, under Grant No. DE-FG02-07ER46431. The authors acknowledge computational support from the National Energy Research Scientific Computing Center of the U.S. Department of Energy.
All Science Journal Classification (ASJC) codes
- General Materials Science
- Physics and Astronomy (miscellaneous)