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Kim YJ, Mendes JL, Michelsen JM, Shin HJ, Lee N, Choi YJ, Cushing SK. Coherent charge hopping suppresses photoexcited small polarons in ErFeO 3 by antiadiabatic formation mechanism. Sci Adv 2024; 10:eadk4282. [PMID: 38507483 PMCID: PMC10954221 DOI: 10.1126/sciadv.adk4282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 02/13/2024] [Indexed: 03/22/2024]
Abstract
Polarons are prevalent in condensed matter systems with strong electron-phonon coupling. The adiabaticity of the polaron relates to its transport properties and spatial extent. To date, only adiabatic small polaron formation has been measured following photoexcitation. The lattice reorganization energy is large enough that the first electron-optical phonon scattering event creates a small polaron without requiring substantial carrier thermalization. We measure that frustrating the iron-centered octahedra in the rare-earth orthoferrite ErFeO3 leads to antiadiabatic polaron formation. Coherent charge hopping between neighboring Fe3+─Fe2+ sites is measured with transient extreme ultraviolet spectroscopy and lasts several picoseconds before the polaron forms. The resulting small polaron formation time is an order of magnitude longer than previous measurements and indicates a shallow potential well, even in the excited state. The results emphasize the importance of considering dynamic electron-electron correlations, not just electron-phonon-induced lattice changes, for small polarons for transport, catalysis, and photoexcited applications.
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Affiliation(s)
- Ye-Jin Kim
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Jocelyn L. Mendes
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Jonathan M. Michelsen
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Hyun Jun Shin
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Nara Lee
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Young Jai Choi
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Scott K. Cushing
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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Liu H, Michelsen JM, Mendes JL, Klein IM, Bauers SR, Evans JM, Zakutayev A, Cushing SK. Measuring Photoexcited Electron and Hole Dynamics in ZnTe and Modeling Excited State Core-Valence Effects in Transient Extreme Ultraviolet Reflection Spectroscopy. J Phys Chem Lett 2023; 14:2106-2111. [PMID: 36802601 DOI: 10.1021/acs.jpclett.2c03894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Transient extreme ultraviolet (XUV) spectroscopy is becoming a valuable tool for characterizing solar energy materials because it can separate photoexcited electron and hole dynamics with element specificity. Here, we use surface-sensitive femtosecond XUV reflection spectroscopy to separately measure photoexcited electron, hole, and band gap dynamics of ZnTe, a promising photocathode for CO2 reduction. We develop an ab initio theoretical framework based on density functional theory and the Bethe-Salpeter equation to robustly assign the complex transient XUV spectra to the material's electronic states. Applying this framework, we identify the relaxation pathways and quantify their time scales in photoexcited ZnTe, including subpicosecond hot electron and hole thermalization, surface carrier diffusion, ultrafast band gap renormalization, and evidence of acoustic phonon oscillations.
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Affiliation(s)
- Hanzhe Liu
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Jonathan M Michelsen
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Jocelyn L Mendes
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Isabel M Klein
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Sage R Bauers
- Materials Science Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Jake M Evans
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Andriy Zakutayev
- Materials Science Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Scott K Cushing
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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