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Photoexcitation
About: Photoexcitation is a research topic. Over the lifetime, 5874 publications have been published within this topic receiving 134733 citations.
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TL;DR: By employing optical pump terahertz (THz) probe spectroscopy, a three dimensional (3D) Dirac semimetal, Cd3As2 film, was investigated systematically at room temperature as discussed by the authors.
Abstract: By employing optical pump Terahertz (THz) probe spectroscopy, a three dimensional (3D) Dirac semimetal, Cd3As2 film, was investigated systematically at room temperature. After photoexcitation at 400/800 nm, the rise time of photoenhanced THz photoconductivity (PC) is about ∼1.0 ps, increasing slightly with the pump fluence, in which time scale, photoexcited electrons and holes establish separate Fermi distribution with electrons in the conduction band and holes in the valence band via fast carrier-carrier scattering and carrier-phonon coupling. The subsequent THz PC relaxation shows single exponential decay with a time constant of ∼6.0 ps that is independent of pump fluence. The relaxation process is dominated by the electron-hole recombination via a radiative and nonradiative way, which is mediated by the phonon-phonon scattering. The optically induced THz complex PC can be well fitted with the Drude-Smith model. Our experimental results shed light on understanding the photocarrier dynamics of the 3D Dirac semimetal materials at THz frequency.
47 citations
TL;DR: In this paper, spectral evidence of the efficient photogeneration of triplet-state excitations in poly(3-alkylthiophene), P3AT, solutions is presented.
Abstract: We present spectral evidence of the efficient photogeneration of triplet‐state excitations in poly(3‐alkylthiophene), P3AT, solutions. The steady‐state photoinduced absorption spectra display a PIA band centered at 1.50 eV which is attributed to a dipole‐allowed triplet–triplet transition. Photoexcitation of P3AT solutions containing C60, results in an efficient energy transfer reaction and provides an estimate for the P3AT triplet‐state energy of 1.57–1.72 eV.
47 citations
TL;DR: In this paper, the authors verified the ultrafast charge transfer dynamics in CsPbBr3 (CPB) quantum dot (QD)-4,5-dibromofluorescein (DBF) composite materials, which form a strong CT complex in the ground state and can absorb more photons in the red region of the solar spectrum.
Abstract: Ultrafast charge-transfer (CT) dynamics has been verified in CsPbBr3 (CPB) quantum dot (QD)–4,5-dibromofluorescein (DBF) composite materials, which form a strong CT complex in the ground state and can absorb more photons in the red region of the solar spectrum. Cyclic voltammetry and steady state luminescence studies suggest that the conduction (CB) and valence bands (VB) of CPB lie, respectively, below the LUMO and the HOMO of the DBF molecule. Steady state and time-resolved luminescence measurements with selective photoexcitation reveal the photoexcited hole transfer from CPB QDs to the DBF molecule, which is thermodynamically viable. Additionally, a red-shifted PL band was detected upon excitation of the CT complex that has been attributed to CT luminescence. Femtosecond transient absorption measurements have been performed to measure the hole transfer and direct electron transfer processes in the composite system and have been measured to be 1–1.25 ps and <100 fs, respectively. Dual behavior of the DB...
47 citations
TL;DR: This work studied a molecular chromophore under strong coupling with the optical mode of a Fabry–Perot cavity resonant to the first electronic absorption band to provide new physical insight into the role of two-particle polaritonic states in explaining transient signatures in hybrid light–matter coupling systems consistent with analogous many-body systems.
Abstract: Strong light-matter coupling is emerging as a fascinating way to tune optical properties and modify the photophysics of molecular systems. In this work, we studied a molecular chromophore under strong coupling with the optical mode of a Fabry-Perot cavity resonant to the first electronic absorption band. Using femtosecond pump-probe spectroscopy, we investigated the transient response of the cavity-coupled molecules upon photoexcitation resonant to the upper and lower polaritons. We identified an excited state absorption from upper and lower polaritons to a state at the energy of the second cavity mode. Quantum mechanical calculations of the many-molecule energy structure of cavity polaritons suggest assignment of this state as a two-particle polaritonic state with optically allowed transitions from the upper and lower polaritons. We provide new physical insight into the role of two-particle polaritonic states in explaining transient signatures in hybrid light-matter coupling systems consistent with analogous many-body systems.
47 citations
TL;DR: In this paper, the photo-induced demagnetization of a ferromagnetic perovskite was investigated by femtosecond pump-probe spectroscopy, where the photoexcitation was observed independently of the quasiparticle relaxation dynamics.
Abstract: Photoinduced effect in a ferromagnetic perovskite ${\mathrm{La}}_{0.6}{\mathrm{Sr}}_{0.4}{\mathrm{MnO}}_{3}$ was investigated by femtosecond pump-probe spectroscopy. By utilizing magneto-optical Kerr rotation as a probe, the photoinduced dynamics of the spins was observed independently of the quasiparticle relaxation dynamics. The low-energy optical conductivity decreases immediately after photoexcitation without changing magnetization, and subsequently the demagnetization occurs in a strongly temperature-dependent manner. The photoinduced demagnetization shows critical slowing down with the time constant up to 1.4 ns when the spin temperature after photoexcitation reaches near the Curie temperature. Such a slow response of a spin system indicates good thermal insulation between quasiparticles and a spin system, suggesting small spin-orbit interaction.
47 citations