Spectral dynamics of shift current in ferroelectric semiconductor SbSI
| Autor: | Yong Zhang, Naoto Nagaosa, Yoshio Kaneko, Jun Fujioka, Naoki Ogawa, Takahiro Morimoto, Masao Nakamura, Masashi Kawasaki, M. Sotome, Y. Tokura, M. Ogino |
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| Rok vydání: | 2019 |
| Předmět: |
Materials science
bulk matter Band gap Terahertz radiation Physics::Optics 02 engineering and technology Electron 01 natural sciences Condensed Matter::Materials Science 0103 physical sciences 010306 general physics Photocurrent Multidisciplinary business.industry Condensed Matter::Mesoscopic Systems and Quantum Hall Effect 021001 nanoscience & nanotechnology ferroelectricity Photoexcitation Applied Physical Sciences picosecond techniques Semiconductor Atomic electron transition Physical Sciences solar cells photovoltaic effect Atomic physics 0210 nano-technology business Excitation |
| Zdroj: | Proceedings of the National Academy of Sciences of the United States of America |
| ISSN: | 1091-6490 0027-8424 |
| DOI: | 10.1073/pnas.1802427116 |
| Popis: | Significance Shift current is one of the bulk photovoltaic phenomena in the materials without inversion symmetry, originating from the geometric Berry phase of the constituting electron bands. This concept of photocurrent generation based on the real-space shift of the electron cloud on the short timescale of optical transition is distinct from that of conventional p–n junction photovoltaics, where the carriers are driven by the built-in Coulomb potential. We experimentally demonstrate for a ferroelectric polar semiconductor how the subpicosecond charge swing on the relevant chemical bond changes its dynamics while scanning the excitation photon energy across the bandgap. On the interband photoexcitation above the bandgap, a finite net charge flow is produced along the electrically polar direction. Photoexcitation in solids brings about transitions of electrons/holes between different electronic bands. If the solid lacks an inversion symmetry, these electronic transitions support spontaneous photocurrent due to the geometric phase of the constituting electronic bands: the Berry connection. This photocurrent, termed shift current, is expected to emerge on the timescale of primary photoexcitation process. We observe ultrafast evolution of the shift current in a prototypical ferroelectric semiconductor antimony sulfur iodide (SbSI) by detecting emitted terahertz electromagnetic waves. By sweeping the excitation photon energy across the bandgap, ultrafast electron dynamics as a source of terahertz emission abruptly changes its nature, reflecting a contribution of Berry connection on interband optical transition. The shift excitation carries a net charge flow and is followed by a swing over of the electron cloud on a subpicosecond timescale. Understanding these substantive characters of the shift current with the help of first-principles calculation will pave the way for its application to ultrafast sensors and solar cells. |
| Databáze: | OpenAIRE |
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