1
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Dringoli BJ, Sutton M, Luo Z, Kanatzidis MG, Cooke DG. Ultrafast Photoinduced Phase Change in SnSe. PHYSICAL REVIEW LETTERS 2024; 132:146901. [PMID: 38640370 DOI: 10.1103/physrevlett.132.146901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 11/21/2023] [Accepted: 01/31/2024] [Indexed: 04/21/2024]
Abstract
Time-resolved multiterahertz (THz) spectroscopy is used to observe an ultrafast, nonthermal electronic phase change in SnSe driven by interband photoexcitation with 1.55 eV pump photons. The transient THz photoconductivity spectrum is found to be Lorentzian-like, indicating charge localization and phase segregation. The rise of photoconductivity is bimodal in nature, with both a fast and slow component due to excitation into multiple bands and subsequent intervalley scattering. The THz conductivity magnitude, dynamics, and spectra show a drastic change in character at a critical excitation fluence of approximately 6 mJ/cm^{2} due to a photoinduced phase segregation and a macroscopic collapse of the band gap.
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Affiliation(s)
| | - Mark Sutton
- Department of Physics, McGill University, Montreal, Quebec H3A2T8, Canada
| | - Zhongzhen Luo
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
- Key Laboratory of Eco-Materials Advanced Technology, College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108, People's Republic of China
| | | | - David G Cooke
- Department of Physics, McGill University, Montreal, Quebec H3A2T8, Canada
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2
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Fujimoto T, Kurihara T, Murotani Y, Tamaya T, Kanda N, Kim C, Yoshinobu J, Akiyama H, Kato T, Matsunaga R. Observation of Terahertz Spin Hall Conductivity Spectrum in GaAs with Optical Spin Injection. PHYSICAL REVIEW LETTERS 2024; 132:016301. [PMID: 38242663 DOI: 10.1103/physrevlett.132.016301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 11/21/2023] [Indexed: 01/21/2024]
Abstract
We report the first observation of the spin Hall conductivity spectrum in GaAs at room temperature. Our terahertz polarimetry with a precision of several μrads resolves the Faraday rotation of terahertz pulses arising from the inverse spin Hall effect of optically injected spin-polarized electrons. The obtained spin Hall conductivity spectrum exhibits an excellent quantitative agreement with theory, demonstrating a crossover in the dominant origin from impurity scattering in the dc regime to the intrinsic Berry-curvature mechanism in the terahertz regime. Our spectroscopic technique opens a new pathway to analyze anomalous transports related to spin, valley, or orbital degrees of freedom.
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Affiliation(s)
- Tomohiro Fujimoto
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Takayuki Kurihara
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Yuta Murotani
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Tomohiro Tamaya
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Natsuki Kanda
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Changsu Kim
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Jun Yoshinobu
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Hidefumi Akiyama
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Takeo Kato
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Ryusuke Matsunaga
- The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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Bulgakova V, Chizhov P, Ushakov A, Ratnikov P, Goncharov Y, Martyanov A, Kononenko V, Savin S, Golovnin I, Konov V, Garnov S. Optical Pump-Terahertz Probe Diagnostics of the Carrier Dynamics in Diamonds. MATERIALS (BASEL, SWITZERLAND) 2023; 17:119. [PMID: 38203973 PMCID: PMC10779634 DOI: 10.3390/ma17010119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 12/21/2023] [Accepted: 12/22/2023] [Indexed: 01/12/2024]
Abstract
Diamond is a promising material for terahertz applications. In this work, we use a non-invasive optical pump-terahertz probe method to experimentally study the photoinduced carrier dynamics in doped diamond monocrystals and a new diamond-silicon composite. The chemical vapor deposited diamond substrate with embedded silicon microparticles showed two photoinduced carrier lifetimes (short lifetime on the order of 4 ps and long lifetime on the order of 200 ps). The short lifetime is several times less than in boron-doped diamonds and nitrogen-doped diamonds which were grown using a high temperature-high pressure technique. The observed phenomenon is explained by the transport of photoexcited carriers across the silicon-diamond interface, resulting in dual relaxation dynamics. The observed phenomenon could be used for ultrafast flexible terahertz modulation.
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Affiliation(s)
- Vladislava Bulgakova
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia; (P.C.)
| | - Pavel Chizhov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia; (P.C.)
- Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Russia
| | - Alexander Ushakov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia; (P.C.)
| | - Pavel Ratnikov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia; (P.C.)
| | - Yuri Goncharov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia; (P.C.)
| | - Artem Martyanov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia; (P.C.)
| | - Vitali Kononenko
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia; (P.C.)
| | - Sergey Savin
- Nanocenter MIREA, MIREA—Russian Technological University, 119454 Moscow, Russia
| | - Ilya Golovnin
- Faculty of Physics, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Vitaly Konov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia; (P.C.)
| | - Sergey Garnov
- Prokhorov General Physics Institute of the Russian Academy of Sciences, 119991 Moscow, Russia; (P.C.)
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Di Virgilio L, Geuchies JJ, Kim H, Krewer K, Wang H, Grechko M, Bonn M. Controlling the electro-optic response of a semiconducting perovskite coupled to a phonon-resonant cavity. LIGHT, SCIENCE & APPLICATIONS 2023; 12:183. [PMID: 37491336 PMCID: PMC10368682 DOI: 10.1038/s41377-023-01232-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 07/10/2023] [Accepted: 07/14/2023] [Indexed: 07/27/2023]
Abstract
Optical cavities, resonant with vibrational or electronic transitions of material within the cavity, enable control of light-matter interaction. Previous studies have reported cavity-induced modifications of chemical reactivity, fluorescence, phase behavior, and charge transport. Here, we explore the effect of resonant cavity-phonon coupling on the transient photoconductivity in a hybrid organic-inorganic perovskite. To this end, we measure the ultrafast photoconductivity response of perovskite in a tunable Fabry-Pérot terahertz cavity, designed to be transparent for optical excitation. The terahertz-cavity field-phonon interaction causes apparent Rabi splitting between the perovskite phonon mode and the cavity mode. We explore whether the cavity-phonon interaction affects the material's electron-phonon interaction by determining the charge-carrier mobility through photoconductivity. Despite the apparent hybridization of cavity and phonon modes, we show that the perovskite properties in both ground (phonon response) and excited (photoconductive response) states remain unaffected by the tunable light-matter interaction. Yet the response of the integral perovskite-terahertz optical cavity system depends critically on the interaction strength of the cavity with the phonon: the transient terahertz response to optical excitation can be increased up to threefold by tuning the cavity-perovskite interaction strength. These results enable tunable switches and frequency-controlled induced transparency devices.
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Affiliation(s)
- Lucia Di Virgilio
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Jaco J Geuchies
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Heejae Kim
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
- Pohang University of Science and Technology, Department of Physics, 37673, Pohang, Korea
| | - Keno Krewer
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Hai Wang
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany
| | - Maksim Grechko
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
| | - Mischa Bonn
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
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Zywitzki D, Mitoraj D, Vilk Y, Mendoza Reyes O, Schleuning M, Friedrich D, Sadlo A, Rogalla D, Eichberger R, Beranek R, Devi A. CVD grown GaSb xN 1-x films as visible-light active photoanodes. Dalton Trans 2021; 50:14832-14841. [PMID: 34596651 DOI: 10.1039/d1dt02455h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The III-V semiconductor GaN is a promising material for photoelectrochemical (PEC) cells, however the large bandgap of 3.45 eV is a considerable hindrance for the absorption of visible light. Therefore, the substitution of small amounts of N anions by isovalent Sb is a promising route to lower the bandgap and thus increase the PEC activity under visible light. Herein we report a new chemical vapor deposition (CVD) process utilizing the precursors bis(N,N'-diisopropyl-2-methyl-amidinato)-methyl gallium (III) and triphenyl antimony (TPSb) for the growth of GaSbxN1-x alloys. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements show crystalline and homogeneous thin films at deposition temperatures in the range of 500-800 °C. Rutherford backscattering spectrometry (RBS) combined with nuclear reaction analysis (NRA) shows an incorporation of 0.2-0.7 at% antimony into the alloy, which results in a slight bandgap decrease (up to 0.2 eV) accompanied by enhanced sub-bandgap optical response. While the resulting photoanodes are active under visible light, the external quantum efficiencies remained low. Intriguingly, the best performing films exhibits the lowest charge carrier mobility according to time resolved THz spectroscopy (TRTS) and microwave conductivity (TRMC) measurements, which showed mobilities of up to 1.75 cm2 V-1 s-1 and 1.2 × 10-2 cm2 V-1 s-1, for each timescale, respectively.
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Affiliation(s)
- Dennis Zywitzki
- Inorganic Materials Chemistry, Ruhr University Bochum, Universitätsstr. 150, 44801 Bochum, Germany.
| | - Dariusz Mitoraj
- Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, 89081 Ulm, Germany
| | - Yury Vilk
- Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, 89081 Ulm, Germany
| | - Oliver Mendoza Reyes
- Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, 89081 Ulm, Germany
| | - Markus Schleuning
- Helmholtz-Zentrum Berlin for Materials and Energy, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Dennis Friedrich
- Helmholtz-Zentrum Berlin for Materials and Energy, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Alexander Sadlo
- Inorganic Materials Chemistry, Ruhr University Bochum, Universitätsstr. 150, 44801 Bochum, Germany.
| | - Detlef Rogalla
- RUBION, Ruhr University Bochum, Universitätsstr. 150, 44801 Bochum, Germany
| | - Rainer Eichberger
- Helmholtz-Zentrum Berlin for Materials and Energy, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
| | - Radim Beranek
- Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, 89081 Ulm, Germany
| | - Anjana Devi
- Inorganic Materials Chemistry, Ruhr University Bochum, Universitätsstr. 150, 44801 Bochum, Germany.
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6
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Theory of Time-Resolved Optical Conductivity of Superconductors: Comparing Two Methods for Its Evaluation. CONDENSED MATTER 2019. [DOI: 10.3390/condmat4030079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Time-resolved optical conductivity is an often used tool to interrogate quantum materials driven out of equilibrium. Theoretically calculating this observable is a complex topic with several approaches discussed in the literature. Using a nonequilibrium Keldysh formalism and a functional derivative approach to the conductivity, we present a comparison of two particular approaches to the calculation of the optical conductivity and their distinguishing features, as applied to a pumped superconductor. The two methods are distinguished by the relative motion of the probe and gate times; either the probe or gate time is kept fixed while the other is swept. We find that both the methods result in same qualitative features of the time-resolved conductivity after pump is over. However, calculating the conductivity by keeping the gate fixed removes artifacts inherent to the other method. We provide software that, based on data for the first method, is able to construct the second approach.
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7
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Thomson MD, Rabia K, Meng F, Bykov M, van Smaalen S, Roskos HG. Phase-channel dynamics reveal the role of impurities and screening in a quasi-one-dimensional charge-density wave system. Sci Rep 2017; 7:2039. [PMID: 28515446 PMCID: PMC5435704 DOI: 10.1038/s41598-017-02198-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 04/12/2017] [Indexed: 11/17/2022] Open
Abstract
Charge density waves (CDWs), i.e. the periodic spatial modulation of coupled electronic and lattice density, are ubiquitous in low-dimensional conductors and have taken on renewed relevance due their role in state-of-the-art materials, e.g. high-Tc superconductors, topological insulators and low-dimensional carbon. As CDWs are described by a complex order parameter to represent both the amplitude and phase, they are formally analogous to BCS superconductors and spin-waves, providing a prototype of collective phenomena for the further development of field theories and ab-initio calculations of complex solids. The low-energy excitations are mixed electron-phonon quanta which ideally separate into an amplitude and phase channel, and provide a sensitive probe of the ground state and non-equilibrium dynamics, including ultrafast photoinduced phase transitions. While recent studies of the amplitude modes have brought substantial progress aided by a phenomenological Ginzburg-Landau framework, we focus here on the phase modes using ultrafast terahertz spectroscopy. Experiments on K0.3MoO3 provide a more complete picture, and reveal a high sensitivity to interactions with impurities and screening effects from photogenerated carriers, both of which can be accounted for by generalizations of the model. Moreover, our considerations emphasize the need to revisit the treatment of inherent electronic damping in quantum-mechanical CDW theories.
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Affiliation(s)
- M D Thomson
- Physikalisches Institut, J. W. Goethe-Universität, 60438, Frankfurt am Main, Germany.
| | - K Rabia
- Physikalisches Institut, J. W. Goethe-Universität, 60438, Frankfurt am Main, Germany
| | - F Meng
- Physikalisches Institut, J. W. Goethe-Universität, 60438, Frankfurt am Main, Germany
| | - M Bykov
- Laboratory of Crystallography, University of Bayreuth, 95440, Bayreuth, Germany
| | - S van Smaalen
- Laboratory of Crystallography, University of Bayreuth, 95440, Bayreuth, Germany
| | - H G Roskos
- Physikalisches Institut, J. W. Goethe-Universität, 60438, Frankfurt am Main, Germany.
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8
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Guo X, Chen H, Wen X, Zheng J. Electron-phonon interactions in MoS2 probed with ultrafast two-dimensional visible/far-infrared spectroscopy. J Chem Phys 2015; 142:212447. [DOI: 10.1063/1.4921573] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Xunmin Guo
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005-1892, USA
| | - Hailong Chen
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005-1892, USA
| | - Xiewen Wen
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005-1892, USA
| | - Junrong Zheng
- Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005-1892, USA
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9
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Hamm P. 2D-Raman-THz spectroscopy: a sensitive test of polarizable water models. J Chem Phys 2015; 141:184201. [PMID: 25399140 DOI: 10.1063/1.4901216] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
In a recent paper, the experimental 2D-Raman-THz response of liquid water at ambient conditions has been presented [J. Savolainen, S. Ahmed, and P. Hamm, Proc. Natl. Acad. Sci. U. S. A. 110, 20402 (2013)]. Here, all-atom molecular dynamics simulations are performed with the goal to reproduce the experimental results. To that end, the molecular response functions are calculated in a first step, and are then convoluted with the laser pulses in order to enable a direct comparison with the experimental results. The molecular dynamics simulation are performed with several different water models: TIP4P/2005, SWM4-NDP, and TL4P. As polarizability is essential to describe the 2D-Raman-THz response, the TIP4P/2005 water molecules are amended with either an isotropic or a anisotropic polarizability a posteriori after the molecular dynamics simulation. In contrast, SWM4-NDP and TL4P are intrinsically polarizable, and hence the 2D-Raman-THz response can be calculated in a self-consistent way, using the same force field as during the molecular dynamics simulation. It is found that the 2D-Raman-THz response depends extremely sensitively on details of the water model, and in particular on details of the description of polarizability. Despite the limited time resolution of the experiment, it could easily distinguish between various water models. Albeit not perfect, the overall best agreement with the experimental data is obtained for the TL4P water model.
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Affiliation(s)
- Peter Hamm
- Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
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10
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Direct observation of the collapse of the delocalized excess electron in water. Nat Chem 2014; 6:697-701. [PMID: 25054939 DOI: 10.1038/nchem.1995] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 06/04/2013] [Indexed: 12/26/2022]
Abstract
It is generally assumed that the hydrated electron occupies a quasi-spherical cavity surrounded by only a few water molecules in its equilibrated state. However, in the very moment of its generation, before water has had time to respond to the extra charge, it is expected to be significantly larger in size. According to a particle-in-a-box picture, the frequency of its absorption spectrum is a sensitive measure of the initial size of the electronic wavefunction. Here, using transient terahertz spectroscopy, we show that the excess electron initially absorbs in the far-infrared at a frequency for which accompanying ab initio molecular dynamics simulations estimate an initial delocalization length of ≈ 40 Å. The electron subsequently shrinks due to solvation and thereby leaves the terahertz observation window very quickly, within ≈ 200 fs.
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11
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Ahmed S, Savolainen J, Hamm P. The effect of the Gouy phase in optical-pump-THz-probe spectroscopy. OPTICS EXPRESS 2014; 22:4256-4266. [PMID: 24663749 DOI: 10.1364/oe.22.004256] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We show theoretically as well as experimentally that the Gouy-phase shift, which depends on the exact positioning of a sample in relation to the focus of a probe beam in a pump-probe experiment, may have a pronounced effect on the shape of the pump-probe signal. The effect occurs only when single-cycle probe pulses are used, i.e. when the slowly varying envelope approximation breaks down, while it disappears for multi-cycle pulses. The effect is thus most relevant in THz time-resolved spectroscopy, where such single cycle pulses are most commonly used, but it should not be overlooked also in other spectral regimes when correspondingly short pulses are involved.
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12
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Ahmed S, Savolainen J, Hamm P. Detectivity enhancement in THz electrooptical sampling. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2014; 85:013114. [PMID: 24517752 DOI: 10.1063/1.4862657] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We demonstrate and discuss a simple scheme that significantly enhances the detectivity of THz electro-optical sampling by introducing a sequence of Brewster windows that increases the ellipticity of the probe beam. By varying the window material or the number of Brewster windows, the enhancement factor can be adjusted; we demonstrate an enhancement factor of ≈20 with four ZnSe Brewster windows. The scheme is particularly useful when very small THz fields are to be measured in connection with low-repetition rate amplified Ti:S laser systems.
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Affiliation(s)
- Saima Ahmed
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Janne Savolainen
- Department of Chemistry, University of Zurich, Zurich, Switzerland
| | - Peter Hamm
- Department of Chemistry, University of Zurich, Zurich, Switzerland
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13
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Abstract
Two-dimensional Raman-terahertz (THz) spectroscopy is presented as a multidimensional spectroscopy directly in the far-IR regime. The method is used to explore the dynamics of the collective intermolecular modes of liquid water at ambient temperatures that emerge from the hydrogen-bond networks water forming. Two-dimensional Raman-THz spectroscopy interrogates these modes twice and as such can elucidate couplings and inhomogeneities of the various degrees of freedoms. An echo in the 2D Raman-THz response is indeed identified, indicating that a heterogeneous distribution of hydrogen-bond networks exists, albeit only on a very short 100-fs timescale. This timescale appears to be too short to be compatible with more extended, persistent structures assumed within a two-state model of water.
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15
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Macutkevic J, Seliuta D, Valusis G, Adomavicius R, Kuzhir P, Paddubskaya A, Shuba M, Maksimenko S, Coderoni L, Micciulla F, Sacco I, Bellucci S. Terahertz time domain spectroscopy of epoxy resin composite with various carbon inclusions. Chem Phys 2012. [DOI: 10.1016/j.chemphys.2012.02.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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16
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Affiliation(s)
- Jason B. Baxter
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania, 19104, United States
| | - Glenn W. Guglietta
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania, 19104, United States
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17
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Charge transport in nanostructured materials for solar energy conversion studied by time-resolved terahertz spectroscopy. J Photochem Photobiol A Chem 2010. [DOI: 10.1016/j.jphotochem.2010.08.006] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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18
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v. Laarhoven HA, Flipse CFJ, Koeberg M, Bonn M, Hendry E, Orlandi G, Jurchescu OD, Palstra TTM, Troisi A. On the mechanism of charge transport in pentacene. J Chem Phys 2008; 129:044704. [DOI: 10.1063/1.2955462] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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19
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Kampfrath T, Gericke DO, Perfetti L, Tegeder P, Wolf M, Frischkorn C. Long- and short-lived electrons with anomalously high collision rates in laser-ionized gases. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:066401. [PMID: 18233926 DOI: 10.1103/physreve.76.066401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Indexed: 05/25/2023]
Abstract
Ultrashort broadband terahertz pulses are applied to probe the electron dynamics of gaseous Ar and O2 following ionization by an intense femtosecond laser pulse. The conductivity in the plasma center is extracted by a modified Wentzel-Kramers-Brillouin approach. It exhibits a nearly perfect Drude-like spectral shape and yields the temporal evolution of the free-electron density and collision rate. While the electron density in the Ar plasma remains nearly constant during the first 200ps after generation, it decays much faster in O2 due to dissociative recombination which is only possible in molecular plasmas. Adding a small amount of the electron scavenger SF6 to Ar reduces the electron lifetime in the plasma dramatically and allows us to determine the electron temperature to about 20,000K . Furthermore, anomalously high, metal-like electron collision rates of up to 25THz are found. Kinetic plasma theory substantially underestimates these rates pointing towards additional and more complex processes randomizing the total electronic momentum. Our results are relevant to both lightning control and generation of terahertz radiation by intense laser pulses in gases.
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Affiliation(s)
- Tobias Kampfrath
- Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
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20
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Kitagawa J, Kadoya Y, Tsubota M, Iga F, Takabatake T. Terahertz conductivity of localized photoinduced carriers in a Mott insulator YTiO(3) at low excitation density, contrasted with the metallic nature in a band semiconductor Si. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:406224. [PMID: 22049122 DOI: 10.1088/0953-8984/19/40/406224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We performed optical-pump terahertz-probe measurements of a Mott insulator YTiO(3) and a band semiconductor Si using a laser diode (1.47 eV) and a femtosecond-pulse laser (1.55 eV). Both samples possess long energy-relaxation times (1.5 ms for YTiO(3) and 15 µs for Si); therefore, it is possible to extract terahertz complex conductivities of photoinduced carriers under equilibrium. We observed highly contrasting behaviour-Drude conductivity in Si and localized conductivity possibly obeying the Jonscher law in YTiO(3). The carrier number at the highest carrier-concentration layer in YTiO(3) is estimated to be 0.015 per Ti site. Anisotropic conductivity of YTiO(3) is determined. Our study indicates that localized carriers might play an important role in the incipient formation of photoinduced metallic phases in Mott insulators. In addition, this study shows that the transfer-matrix method is effective for extracting an optical constant of a sample with a spatially inhomogeneous carrier distribution.
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Affiliation(s)
- J Kitagawa
- Department of Quantum Matter, ADSM, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530, Japan
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Schins JM, Hendry E, Bonn M, Muller HG. Retrieving the susceptibility from time-resolved terahertz experiments. J Chem Phys 2007; 127:094308. [PMID: 17824740 DOI: 10.1063/1.2761915] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present an analytical expression for the observed signal in time- and phase-resolved pump-probe studies, with particular emphasis on terahertz time-domain spectroscopy. Maxwell's equations are solved for the response of damped, harmonic oscillators to a driving probe field in the perturbative regime. Our analytical expressions agree with the one previously reported in the literature [Nemec et al., J. Chem. Phys. 122, 104503 (2005)] in the Drude limit; however, they differ in the case of a vibrational resonance.
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Affiliation(s)
- J M Schins
- Opto-Electronic Materials Section, DelftChem Tech, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
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Kuzel P, Kadlec F, Nĕmec H. Propagation of terahertz pulses in photoexcited media: Analytical theory for layered systems. J Chem Phys 2007; 127:024506. [PMID: 17640136 DOI: 10.1063/1.2748402] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Optical pump-terahertz probe spectroscopy has become a widely used experimental tool for the investigation of the ultrafast far-infrared response of polar systems. In this paper the authors present an analytical method of calculating the propagation of ultrashort terahertz pulses in photoexcited media. The transient terahertz wave form transmitted through the sample is equal to a product of the incident terahertz field (at a mixed frequency), transient susceptibility, and a so called transfer function which depends on the properties of the sample in equilibrium. The form of the transfer function is derived for general layered systems and for specific cases including one-dimensional photonic crystals, thin films, and bulk samples. Simplified expressions directly applicable to the analysis of the experimental results related to the most common sample geometries are shown and discussed.
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Affiliation(s)
- P Kuzel
- Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
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Nĕmec H, Kadlec F, Kadlec C, Kuzel P, Jungwirth P. Ultrafast far-infrared dynamics probed by terahertz pulses: A frequency-domain approach. II. Applications. J Chem Phys 2005; 122:104504. [PMID: 15836329 DOI: 10.1063/1.1857871] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present data obtained by time-resolved terahertz spectroscopy in selected semiconducting and molecular systems exhibiting subpicosecond far-infrared dynamics. We use a frequency-domain method which eliminates the influence of instrumental functions and artifacts due to frequency mixing and yields a two-dimensional transient conductivity of the photoexcited sample. This technique enables improving the attainable experimental time resolution and allows a simple qualitative interpretation of the results without a priori modeling. The quantitative interpretation is based on the time-dependent Drude and damped harmonic oscillator models.
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Affiliation(s)
- H Nĕmec
- Institute of Physics, Academy of Sciences of the Czech Republic, and Center for Complex Molecular Systems and Biomolecules Na Slovance 2, 182 21 Prague 8, Czech Republic
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Nĕmec H, Kadlec F, Surendran S, Kuzel P, Jungwirth P. Ultrafast far-infrared dynamics probed by terahertz pulses: A frequency domain approach. I. Model systems. J Chem Phys 2005; 122:104503. [PMID: 15836328 DOI: 10.1063/1.1857851] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Time-resolved terahertz spectroscopy has become a widely used experimental tool for the investigation of ultrafast dynamics of polar systems in the far infrared. We have recently proposed an analytical method for the extraction of a transient two-dimensional susceptibility from the experimental data [Nĕmec, Kadlec, and Kuzel, J. Chem. Phys. 117, 8454 (2002)]. In the present paper the methodology of optical pump-terahertz probe experiments is further developed for direct application in realistic experimental situations. The expected two-dimensional transient response function is calculated for a number of model cases (including Drude dynamics of free carriers, harmonic and anharmonic oscillator modes); these results serve as a basis for the interpretation of experimental results. We discuss also the cases where only partial (one-dimensional) information about the system dynamics can be experimentally obtained.
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Affiliation(s)
- H Nĕmec
- Institute of Physics, Academy of Sciences of the Czech Republic, and Center for Complex Molecular Systems and Biomolecules, Na Slovance 2, 182 21 Prague 8, Czech Republic
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Kadlec F, Kuzel P, Coutaz JL. Optical rectification at metal surfaces. OPTICS LETTERS 2004; 29:2674-6. [PMID: 15552681 DOI: 10.1364/ol.29.002674] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The emission of freely propagating terahertz (THz) radiation coming from optical rectification at metallic surfaces has been detected and characterized for the first time to the authors' knowledge. The observed THz transients are induced through nonlinear electronic processes at gold and silver surfaces on intense pulsed optical photoexcitation and exhibit a peak electric field of as much as 200 V/cm. This finding opens a qualitatively new way to investigate nonlinear phenomena at metal surfaces and also can be exploited for the development of new THz emitters.
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Affiliation(s)
- Filip Kadlec
- Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic.
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Affiliation(s)
- Charles A Schmuttenmaer
- Department of Chemistry, Yale University, 225 Prospect Street, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA
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Kadlec F, Kadlec C, Kuzel P, Slavícek P, Jungwirth P. Optical pump–terahertz probe spectroscopy of dyes in solutions: Probing the dynamics of liquid solvent or solid precipitate? J Chem Phys 2004; 120:912-7. [PMID: 15267927 DOI: 10.1063/1.1633256] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The optical pump-terahertz probe spectroscopy was used together with ab initio calculations and molecular dynamics simulations to investigate ultrafast dynamics following electronic excitation of Coumarin 153 and TBNC (2,11,20,29-tetra-tert-butyl-2,3-naphtalocyanine) dyes in polar solvents. By scanning the terahertz waveform for different pump-probe delays this experimental technique allows us to obtain two dimensional spectra directly reflecting the temporal response of the system. A distinct signal was obtained for TBNC in chloroform, 2-propanol, and n-butanol, while no signal was recorded for Coumarin 153 in either of these solvents. We explain the nonequilibrium signal detected in TBNC solutions by the presence of a solid, polycrystalline phase of the dye resulting from irradiating the solution by intense optical pulses.
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Affiliation(s)
- Filip Kadlec
- Institute of Physics, Academy of Sciences of the Czech Republic and Center for Complex Molecular Systems and Biomolecules, Na Slovance 2, 18221 Prague 8, Czech Republic
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