Back to Search
Start Over
Free and defect-bound (bi)polarons in LiNbO3 : Atomic structure and spectroscopic signatures from ab initio calculations
- Source :
- Physical Review Research. 2
- Publication Year :
- 2020
- Publisher :
- American Physical Society (APS), 2020.
-
Abstract
- Polarons in dielectric crystals play a crucial role for applications in integrated electronics and optoelectronics. In this work, we use density-functional theory and Green's function methods to explore the microscopic structure and spectroscopic signatures of electron polarons in lithium niobate (LiNbO3). Total-energy calculations and the comparison of calculated electron paramagnetic resonance data with available measurements reveal the formation of bound polarons at Nb_Li antisite defects with a quasi-Jahn-Teller distorted, tilted configuration. The defect-formation energies further indicate that (bi)polarons may form not only at Nb_Li antisites but also at structures where the antisite Nb atom moves into a neighboring empty oxygen octahedron. Based on these structure models, and on the calculated charge-transition levels and potential-energy barriers, we propose two mechanisms for the optical and thermal splitting of bipolarons, which provide a natural explanation for the reported two-path recombination of bipolarons. Optical-response calculations based on the Bethe-Salpeter equation, in combination with available experimental data and new measurements of the optical absorption spectrum, further corroborate the geometries proposed here for free and defect-bound (bi)polarons.
Details
- ISSN :
- 26431564
- Volume :
- 2
- Database :
- OpenAIRE
- Journal :
- Physical Review Research
- Accession number :
- edsair.doi...........ec2a32118010adad2cae3621d70596d2