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Spectral dynamics of shift current in ferroelectric semiconductor SbSI.

ABSTRACT: 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.

SUBMITTER: Sotome M 

PROVIDER: S-EPMC6369763 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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Spectral dynamics of shift current in ferroelectric semiconductor SbSI.

Sotome M M   Nakamura M M   Fujioka J J   Ogino M M   Kaneko Y Y   Morimoto T T   Zhang Y Y   Kawasaki M M   Nagaosa N N   Tokura Y Y   Ogawa N N  

Proceedings of the National Academy of Sciences of the United States of America 20190122 6

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 sem  ...[more]