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Cited by 138Topological Materials and PhenomenaTerahertz technology and applicationsLaser-Matter Interactions and Applications

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Spectral dynamics of shift current in ferroelectric semiconductor SbSI

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Sotome, M., Nakamura, M., Fujioka, J., Ogino, M., Kaneko, Y., Morimoto, T., Zhang, Y., Kawasaki, M., Nagaosa, N., Tokura, Y., Ogawa, N.·2019·Proceedings of the National Academy of Sciences
DOI 10.1073/pnas.1802427116PMC PMC6369763
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Abstract

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.

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Crossref · 10.1073/pnas.1802427116

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Figures

Fig. 1. Emission of terahertz waves from SbSI. (A) Crystal structure of SbSI. (B) Terahertz waves emitted from SbSI in the ferroelectric phase after ±Ps poling (±2.0 kV/cm, respectively). (C) Temperature dependence of the terahertz waveform (offset for clarity). (D) Temperature dependence of the terahertz intensity plotted together with the pyroelectric polarization. ITHz stands for the frequency integration of the power spectrum in the Fourier space, which is proportional to the square of the source current. Excitation photon energy (ℏωexc) is 2.3 eV (400 nJ), and photon polarization is E(ωexc)∥E(ωTHz)∥c.
Fig. 1. Emission of terahertz waves from SbSI. (A) Crystal structure of SbSI. (B) Terahertz waves emitted from SbSI in the ferroelectric phase after ±Ps poling (±2.0 kV/cm, respectively). (C) Temperature dependence of the terahertz waveform (offset for clarity). (D) Temperature dependence of the terahertz intensity plotted together with the pyroelectric polarization. ITHz stands for the frequency integration of the power spectrum in the Fourier space, which is proportional to the square of the source current. Excitation photon energy (ℏωexc) is 2.3 eV (400 nJ), and photon polarization is E(ωexc)∥E(ωTHz)∥c.CC BY-NC-ND · PubMed Central
Fig. 2. Action spectra of the shift current deduced by the factor analysis. (A) Experimental terahertz waveforms for the excitation above and below the band gap (offset for clarity). (B) Extracted base waveforms by using the factor analysis (covariance matrix calculation) from 22 datasets. (C) Action spectra of shift current (Shift) and in-gap OR at 282 and 300 K (below and above TC, respectively). Error bars reflect the unique variance in the factor analysis, which is smaller than the marker for the case of in-gap OR. The result of the first-principles calculation is also shown. Excitation intensity is 400 nJ in the linear regime to the incident pulse energy, and photon polarization is E(ωexc)∥E(ωTHz)∥c.
Fig. 2. Action spectra of the shift current deduced by the factor analysis. (A) Experimental terahertz waveforms for the excitation above and below the band gap (offset for clarity). (B) Extracted base waveforms by using the factor analysis (covariance matrix calculation) from 22 datasets. (C) Action spectra of shift current (Shift) and in-gap OR at 282 and 300 K (below and above TC, respectively). Error bars reflect the unique variance in the factor analysis, which is smaller than the marker for the case of in-gap OR. The result of the first-principles calculation is also shown. Excitation intensity is 400 nJ in the linear regime to the incident pulse energy, and photon polarization is E(ωexc)∥E(ωTHz)∥c.CC BY-NC-ND · PubMed Central
Fig. 3. Transient nonlinear polarization and carrier dynamics. (A) Schematics of the nonlinear polarization (P), transient current (J), and emitted electric field (Eemit) for the shift current (Shift) and in-gap photoexcitation (in-gap). The detected terahertz electric fields are further modified (Eobs) due to the diffraction and instrumental factors. (B) Retrieved current dynamics for the shift current and in-gap photoexcitation. Solid lines represent the fitting curves. Shift current accompanies a swing over (relaxation) of the charge with a decay time of ∼0.5 ps, whereas the in-gap photoexcitation appears only within the incident pulse duration. (C and D) Temperature and incident photon energy dependence of the decay time τ. Excitation intensity is 400 nJ, and photon polarization is E(ωexc)∥E(ωTHz)∥c.
Fig. 3. Transient nonlinear polarization and carrier dynamics. (A) Schematics of the nonlinear polarization (P), transient current (J), and emitted electric field (Eemit) for the shift current (Shift) and in-gap photoexcitation (in-gap). The detected terahertz electric fields are further modified (Eobs) due to the diffraction and instrumental factors. (B) Retrieved current dynamics for the shift current and in-gap photoexcitation. Solid lines represent the fitting curves. Shift current accompanies a swing over (relaxation) of the charge with a decay time of ∼0.5 ps, whereas the in-gap photoexcitation appears only within the incident pulse duration. (C and D) Temperature and incident photon energy dependence of the decay time τ. Excitation intensity is 400 nJ, and photon polarization is E(ωexc)∥E(ωTHz)∥c.CC BY-NC-ND · PubMed Central
Fig. 4. Incident laser power dependence of terahertz emission and linear optical conductivity. (A) Terahertz absolute amplitude (ITHz^(1/2)) showing sublinear incident power dependence. The solid line is a fit by Eq. 1. Photon polarization is E(ωexc)∥E(ωTHz)∥c. (B) Linear optical conductivity plotted together with the first-principles data (dashed curve; up to 2.7 eV) and fitting curves.
Fig. 4. Incident laser power dependence of terahertz emission and linear optical conductivity. (A) Terahertz absolute amplitude (ITHz^(1/2)) showing sublinear incident power dependence. The solid line is a fit by Eq. 1. Photon polarization is E(ωexc)∥E(ωTHz)∥c. (B) Linear optical conductivity plotted together with the first-principles data (dashed curve; up to 2.7 eV) and fitting curves.CC BY-NC-ND · PubMed Central
Fig. 5. Polarimetry of shift current and in-gap OR. (A) Schematic illustration of the connected polyhedra and definition of angle θ. (B and C) Incident polarization dependence of the pulsed zero-bias photocurrent with excitation photon energy above and below the bandgap, respectively, measured by a transimpedance amplifier through the electrodes at 282 K. The zero degree corresponds to the polarization parallel to the c axis. (D and E) Corresponding amplitude spectra of the emitted terahertz wave (ITHz^(1/2)). The wire-grid analyzer is fixed at E(ωTHz)∥c or E(ωTHz)⊥c, and incident laser polarization is rotated from E(ωexc)∥c. Solid lines represent the fittings considering the symmetry-allowed tensor elements (Eq. 4).
Fig. 5. Polarimetry of shift current and in-gap OR. (A) Schematic illustration of the connected polyhedra and definition of angle θ. (B and C) Incident polarization dependence of the pulsed zero-bias photocurrent with excitation photon energy above and below the bandgap, respectively, measured by a transimpedance amplifier through the electrodes at 282 K. The zero degree corresponds to the polarization parallel to the c axis. (D and E) Corresponding amplitude spectra of the emitted terahertz wave (ITHz^(1/2)). The wire-grid analyzer is fixed at E(ωTHz)∥c or E(ωTHz)⊥c, and incident laser polarization is rotated from E(ωexc)∥c. Solid lines represent the fittings considering the symmetry-allowed tensor elements (Eq. 4).CC BY-NC-ND · PubMed Central

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Metadata

Authors
Sotome, M., Nakamura, M., Fujioka, J., Ogino, M., Kaneko, Y., Morimoto, T., Zhang, Y., Kawasaki, M., Nagaosa, N., Tokura, Y., & Ogawa, N.
Affiliations
  • RIKEN Center for Emergent Matter Science (JP)
  • Japan Science and Technology Agency (JP)
  • The University of Tokyo (JP)
  • University of California, Berkeley (US)
  • Leibniz Institute for Solid State and Materials Research (DE)
Corresponding author
Sotome, M.
ORCID
Venue
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences
Published
2019-01-22
Volume
116
Issue
6
Pages
1929-1933
ISSN
  • 0027-8424 (ISSN-L)
  • 1091-6490
DOI
10.1073/pnas.1802427116
PMC
PMC6369763
OpenAlex
W2785837563
Cited by
138
References
50
Citations by year
2026: 16 · 2025: 17 · 2024: 18 · 2023: 14 · 2022: 20 · 2021: 15 · 2020: 25 · 2019: 12
FWCI
7.91
Type
journal article
Language
en
Open access
Licence
Locations
  • Proceedings of the National Academy of Sciences (publishedVersion, cc-by-nc-nd)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by-nc-nd)
  • PubMed Central (publishedVersion, cc-by-nc-nd)
  • PubMed (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) (submittedVersion)
  • RENATE (submittedVersion, cc-by-nc-nd)
  • MPG.PuRe (Max Planck Society) (submittedVersion)
  • arXiv (Cornell University)
  • RENATE
Funders
  • MEXT | Japan Society for the Promotion of Science (24224009, 16K13705, 17H02914, 16H00981, 18K14155)
  • MEXT | Japan Science and Technology Agency (JPMJPR16R5, JPMJPR15R5, JPMJPR17I3)
  • Deutsche Forschungsgemeinschaft (SFB1143)
Topics
  • Physical Sciences › Physics and Astronomy › Condensed Matter Physics › Topological Materials and Phenomena
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Terahertz technology and applications
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Laser-Matter Interactions and Applications
Keywords
shift current, ferroelectric semiconductors, Berry connection, terahertz emission, ultrafast electron dynamics, interband transitions, inversion symmetry breaking, photoexcitation, spectral dynamics

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