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Lubchenko V, Kurnosov A. Temperature-driven narrowing of the insulating gap as a precursor of the insulator-to-metal transition: Implications for the electronic structure of solids. J Chem Phys 2019; 150:244502. [PMID: 31255083 DOI: 10.1063/1.5063587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a microscopic picture rationalizing the surprisingly steep decrease in the bandgap with temperature in insulators, crystalline or otherwise. The gap narrowing largely results from fluctuations of long-wavelength optical phonons-when the latter are present-or their disordered analogs if the material is amorphous. We elaborate on this notion to show that possibly with the exception of weakly bound solids made of closed-shell electronic configurations, the existence of an insulating gap or pseudogap in a periodic solid implies that optical phonons must be present, too. This means that in an insulating solid, the primitive cell must have at least two atoms and/or that a charge density wave is present, with the possible exception of weakly bonded solids such as rare-gas or ferromagnetic Wigner crystals. As a corollary, a (periodic) elemental solid held together by nonclosed shell interactions and whose primitive unit contains only one atom will ordinarily be a metal, consistent with observation. Consequences of the present picture for Wigner solids are discussed. A simple field theory of the metal-insulator transition is constructed that directly ties long-wavelength optical vibrations with fluctuations of an order parameter for the metal-insulator transition. The order parameter is shown to have at least two components, yet no Goldstone mode arises as a result of the transition.
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Affiliation(s)
- Vassiliy Lubchenko
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA
| | - Arkady Kurnosov
- Department of Chemistry, University of Houston, Houston, Texas 77204-5003, USA
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Khazaeinezhad R, Hosseinzadeh Kassani S, Paulson B, Jeong H, Gwak J, Rotermund F, Yeom DI, Oh K. Ultrafast nonlinear optical properties of thin-solid DNA film and their application as a saturable absorber in femtosecond mode-locked fiber laser. Sci Rep 2017; 7:41480. [PMID: 28128340 PMCID: PMC5269743 DOI: 10.1038/srep41480] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 12/20/2016] [Indexed: 11/29/2022] Open
Abstract
A new extraordinary application of deoxyribonucleic acid (DNA) thin-solid-film was experimentally explored in the field of ultrafast nonlinear photonics. Optical transmission was investigated in both linear and nonlinear regimes for two types of DNA thin-solid-films made from DNA in aqueous solution and DNA-cetyltrimethylammonium chloride (CTMA) in an organic solvent. Z-scan measurements revealed a high third-order nonlinearity with n2 exceeding 10−9 at a wavelength of 1570 nm, for a nonlinarity about five orders of magnitude larger than that of silica. We also demonstrated ultrafast saturable absorption (SA) with a modulation depth of 0.43%. DNA thin solid films were successfully deposited on a side-polished optical fiber, providing an efficient evanescent wave interaction. We built an organic-inorganic hybrid all-fiber ring laser using DNA film as an ultrafast SA and using Erbium-doped fiber as an efficient optical gain medium. Stable transform-limited femtosecond soliton pulses were generated with full width half maxima of 417 fs for DNA and 323 fs for DNA-CTMA thin-solid-film SAs. The average output power was 4.20 mW for DNA and 5.46 mW for DNA-CTMA. Detailed conditions for DNA solid film preparation, dispersion control in the laser cavity and subsequent characteristics of soliton pulses are discussed, to confirm unique nonlinear optical applications of DNA thin-solid-film.
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Affiliation(s)
- Reza Khazaeinezhad
- Photonic Device Physics Laboratory, Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, South Korea.,Harvard Medical School, Boston, Massachusetts 02115, USA.,Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Sahar Hosseinzadeh Kassani
- Photonic Device Physics Laboratory, Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, South Korea.,Harvard Medical School, Boston, Massachusetts 02115, USA.,Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Bjorn Paulson
- Photonic Device Physics Laboratory, Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, South Korea
| | - Hwanseong Jeong
- Department of Physics &Energy Systems Research, Ajou University, Suwon 443-749, South Korea
| | - Jiyoon Gwak
- Department of Physics &Energy Systems Research, Ajou University, Suwon 443-749, South Korea
| | - Fabian Rotermund
- Department of Physics &Energy Systems Research, Ajou University, Suwon 443-749, South Korea.,Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, South Korea
| | - Dong-Il Yeom
- Department of Physics &Energy Systems Research, Ajou University, Suwon 443-749, South Korea
| | - Kyunghwan Oh
- Photonic Device Physics Laboratory, Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, South Korea
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Tyutnev AP, Kundina YE, Saenko VS, Pozhidaev ED. Charge Carrier Transport in Disordered Solids: Dispersive Versus Gaussian. HIGH PERFORM POLYM 2016. [DOI: 10.1177/095400830301500104] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We present a critical review of numerous time-of-flight and radiation-induced conductivity measurements in disordered solids as well as of the theoretical models used to explain them. Recent experiments employing both techniques simultaneously resulted in conflicting conclusions about charge carrier transport in molecularly doped polymers. Whereas the latter method gives a consistent representation of it as a highly non-equilibrium phenomenon of yet unspecified duration (dispersive process), the former is notorious for a number of ambiguous results, some of which are still present, and it is also known to generate the Gaussian disorder model predicting the prevalent steady-state mobility (Gaussian transport). A way to reconcile these seemingly contradictory data has been suggested. This consists of taking due account of surface effects arising from the presence of surface regions (layers) in the dielectric sample with somewhat inferior electronic properties compared with the bulk. Preliminary calculations lend credit to this idea. It is argued that the time-of-flight method should be supplemented by some bulk excitation technique, which allows us to minimize or even remove surface effects. The methodological basis of the former method should be revisited. On the weight of the available information, preference should be given to the dispersive rather than the Gaussian transport but a major problem still exists.
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Affiliation(s)
| | | | | | - Evgenii D. Pozhidaev
- Moscow State Institute of Electronics and Mathematics, Bol. Trechsvyatitel. per, 3/12, Moscow Russia
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Tyutnev AP, Saenko VS, Pozhidaev ED, Kolesnikov VA. Charge Carrier Transport in a Molecularly Doped Polymer: Dispersive versus Gaussian. HIGH PERFORM POLYM 2016. [DOI: 10.1177/0954008305042757] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A typical molecularly doped polymer (bisphenol- A-polycarbonate containing 30 mass% of hydrazone DEH) has been put to thorough experimental examination by both time of flight and radiationinduced conductivity methods. A much improved measurement technique incorporating a computerassisted registration scheme that allows one to record a complete current transient over up to five decades in time in one single shot was employed. Studies of radiation-induced conductivity (conductivity proper as well as transit effects) uniquely prove the dispersive rather than the Gaussian transport of holes (majority carriers) in this polymer. The shape of the time-of flight current transients is strongly influenced by some extraneous factor, presumably surface traps, whose role in radiation-induced conductivity could hardly be detected. We describe the phenomenon quantitatively using a multiple trapping formalism. A critical discussion of the present situation in the field of charge carrier transport in disordered solids is also included.
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Affiliation(s)
| | | | - Evgenii D. Pozhidaev
- Moscow State Institute of Electronics and Mathematics, Bol. Trechsvyatitel. per., 3/12, Moscow, Russia
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Bertoluzzi L, Herraiz-Cardona I, Gottesman R, Zaban A, Bisquert J. Relaxation of Electron Carriers in the Density of States of Nanocrystalline TiO2. J Phys Chem Lett 2014; 5:689-694. [PMID: 26270838 DOI: 10.1021/jz4027584] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Band gap localized states and surface states play a dominant role in the application of nanocrystalline metal oxides to photovoltaics and solar fuel production. Electrons injected in nanocrystalline TiO2 by voltage or photogeneration are mainly located in band gap states. Therefore, charging a nanoparticulate semiconductor network allows one to recover the density of states (DOS) in the energy axis. However, shallow traps remain in equilibrium with the conduction band electrons, while deep traps do not. We show that the characteristic peak of the apparent DOS mixes an exponential DOS and a monoenergetic surface state. A model that incorporates the trap's kinetics proves to be very efficient to assess the important parameters that determine both contributions via variation of charging rate. Contrary to the common theory, we demonstrate that the peculiar capacitance peak of nanocrystalline TiO2 can be mainly attributed, in some cases, to deep traps in the exponential distribution.
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Affiliation(s)
- Luca Bertoluzzi
- †Photovoltaics and Optoelectronic Devices Group, Departament de Fı́sica, Universitat Jaume I, 12071 Castelló, Spain
| | - Isaac Herraiz-Cardona
- †Photovoltaics and Optoelectronic Devices Group, Departament de Fı́sica, Universitat Jaume I, 12071 Castelló, Spain
| | | | | | - Juan Bisquert
- †Photovoltaics and Optoelectronic Devices Group, Departament de Fı́sica, Universitat Jaume I, 12071 Castelló, Spain
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Tyutnev AP, Ikhsanov RS, Saenko VS, Pozhidaev ED. Dispersive transport in molecularly doped polymers: Theory and experiment. RUSS J ELECTROCHEM+ 2012. [DOI: 10.1134/s1023193512020188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Tyutnev AP, Saenko VS, Ikhsanov RS, Pozhidaev ED. A version of the time-of-flight technique with a variable thickness of the generation layer and its use for verification of the type of electronic transport in molecularly doped polymers. POLYMER SCIENCE SERIES A 2009. [DOI: 10.1134/s0965545x0910006x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Tyutnev AP, Saenko VS, Pozhidaev ED, Kolesnikov VA. Verification of the dispersive charge transport in a hydrazone:polycarbonate molecularly doped polymer. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:115107. [PMID: 21693912 DOI: 10.1088/0953-8984/21/11/115107] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We report results of specially planned experiments intended to verify the dispersive character of the charge carrier transport in polycarbonate molecularly doped with hydrazone at 30 wt% loading, using for this purpose samples specifically featuring a well-defined plateau on a linear-linear plot. For this purpose we propose a new variant of the time-of-flight technique which allows easy changing of the generation zone width from about 0.5 µm (surface excitation) through intermediate values to full sample thickness (bulk excitation). To achieve this, we use electron pulses of 3-50 keV energy rather than traditional light pulses provided by lasers. Experimental results corroborated by numerical calculations uniquely prove that carrier transport in this molecularly doped polymer is dispersive, with the dispersion parameter equal to 0.75. Nevertheless, the mobility field dependence follows the famous Poole-Frenkel law.
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Affiliation(s)
- Andrey P Tyutnev
- Moscow State Institute of Electronics and Mathematics, Bol. Trechsvyatitel. per., 3, Moscow 109028, Russia
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Tyutnev AP, Saenko VS, Pozhidaev ED. Universal technique for studying electron transport in polymers. POLYMER SCIENCE SERIES B 2006. [DOI: 10.1134/s1560090406090077] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Affiliation(s)
- G. J. Adriaenssens
- a Katholieke Universiteit Leuven, Laboratorium voor Vaste-Stof-en Hoge-Drukfysika , Celestijnenlaan 200 D, B-3030, Leuven , Belgium
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Electron transport of holes in molecularly doped polycarbonate and its radiation-induced conductivity. HIGH ENERGY CHEMISTRY 2000. [DOI: 10.1007/bf02761834] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Greeff CW, Glyde HR. Anomalous Urbach tail in GaAs. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 51:1778-1783. [PMID: 9978899 DOI: 10.1103/physrevb.51.1778] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Dieckmann A, Bässler H, Borsenberger PM. An assessment of the role of dipoles on the density‐of‐states function of disordered molecular solids. J Chem Phys 1993. [DOI: 10.1063/1.465640] [Citation(s) in RCA: 211] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Klochikhin AA, Ogloblin SG. Density of localized states in disordered solids. PHYSICAL REVIEW. B, CONDENSED MATTER 1993; 48:3100-3115. [PMID: 10008732 DOI: 10.1103/physrevb.48.3100] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Zhou JH, Elliott SR. Long-time photocurrent decay in a-Si:H films: A bulk property. PHYSICAL REVIEW. B, CONDENSED MATTER 1992; 45:1668-1671. [PMID: 10001667 DOI: 10.1103/physrevb.45.1668] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Klinger MI, Kudryavtsev VG, Ryazanov MI, Taraskin SN. Self-trapped single-particle excitations in equilibrium and photoconductivity in glassy semiconductors. PHYSICAL REVIEW. B, CONDENSED MATTER 1989; 40:6311-6320. [PMID: 9992702 DOI: 10.1103/physrevb.40.6311] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Li Q, Soukoulis CM, Economou EN. Universal behavior near the band edges for disordered systems: Numerical and coherent-potential-approximation studies. PHYSICAL REVIEW. B, CONDENSED MATTER 1988; 37:8289-8297. [PMID: 9944165 DOI: 10.1103/physrevb.37.8289] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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John S, Chou MY, Cohen MH, Soukoulis CM. Density of states for an electron in a correlated Gaussian random potential: Theory of the Urbach tail. PHYSICAL REVIEW. B, CONDENSED MATTER 1988; 37:6963-6976. [PMID: 9943966 DOI: 10.1103/physrevb.37.6963] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Ries B, Bässler H, Grünewald M, Movaghar B. Monte Carlo study of relaxation and diffusion in glassy systems. PHYSICAL REVIEW. B, CONDENSED MATTER 1988; 37:5508-5517. [PMID: 9943740 DOI: 10.1103/physrevb.37.5508] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Bacalis N, Economou EN, Cohen MH. Simple derivation of exponential tails in the density of states. PHYSICAL REVIEW. B, CONDENSED MATTER 1988; 37:2714-2717. [PMID: 9944833 DOI: 10.1103/physrevb.37.2714] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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Grein CH, John S. Polaronic band tails in disordered solids: Combined effects of static randomness and electron-phonon interactions. PHYSICAL REVIEW. B, CONDENSED MATTER 1987; 36:7457-7468. [PMID: 9942513 DOI: 10.1103/physrevb.36.7457] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
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John S, Soukoulis C, Cohen MH, Economou EN. Theory of electron band tails and the Urbach optical-absorption edge. PHYSICAL REVIEW LETTERS 1986; 57:1777-1780. [PMID: 10033542 DOI: 10.1103/physrevlett.57.1777] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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