Photoinduced Phase Transitions

Photoinduced Phase Transitions PDF

Author: K. Nasu

Publisher: World Scientific

Published: 2004

Total Pages: 360

ISBN-13: 9789812565723

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A new class of insulating solids was recently discovered. Whenirradiated by a few visible photons, these solids give rise to amacroscopic excited domain that has new structural and electronicorders quite different from the starting ground state. This occurrenceis called photoinduced phase transition, and this multi-authoredbook reviews recent theoretical and experimental studies of this newphenomenon.

Emergent States in Photoinduced Charge-Density-Wave Transitions

Emergent States in Photoinduced Charge-Density-Wave Transitions PDF

Author: Alfred Zong

Publisher: Springer Nature

Published: 2021-09-17

Total Pages: 234

ISBN-13: 3030817512

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This book advances understanding of light-induced phase transitions and nonequilibrium orders that occur in a broken-symmetry system. Upon excitation with an intense laser pulse, materials can undergo a nonthermal transition through pathways different from those in equilibrium. The mechanism underlying these photoinduced phase transitions has long been researched, but many details in this ultrafast, non-adiabatic regime still remain to be clarified. The work in this book reveals new insights into this phenomena via investigation of photoinduced melting and recovery of charge density waves (CDWs). Using several time-resolved diffraction and spectroscopic techniques, the author shows that the light-induced melting of a CDW is characterized by dynamical slowing-down, while the restoration of the symmetry-breaking order features two distinct timescales: A fast recovery of the CDW amplitude is followed by a slower re-establishment of phase coherence, the latter of which is dictated by the presence of topological defects in the CDW. Furthermore, after the suppression of the original CDW by photoexcitation, a different, competing CDW transiently emerges, illustrating how a hidden order in equilibrium can be unleashed by a laser pulse. These insights into CDW systems may be carried over to other broken-symmetry states, such as superconductivity and magnetic ordering, bringing us one step closer towards manipulating phases of matter using a laser pulse.

Photoinduced Phase Transitions and Irreversible Dynamics Studied with Single-shot Spectroscopy

Photoinduced Phase Transitions and Irreversible Dynamics Studied with Single-shot Spectroscopy PDF

Author: Samuel Welch Teitelbaum

Publisher:

Published: 2016

Total Pages: 237

ISBN-13:

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Single-shot femtosecond spectroscopy was developed to study irreversible processes and materials far from equilibrium. It was then applied to investigate photoinduced phase transitions in semimetals and manganites. The dual-echelon single-shot instrument was developed, and noise sources, experimental artifacts, and the fundamental limits of the single-shot technique were explored. In this thesis, advances in the single-shot technique that allow for more detailed investigation of material processes and characterization of far-from-equilibrium dynamics in a wider range of systems are discussed. Experiments and modeling of photoinduced phase transitions in two classes of systems, semimetals and manganites, are presented. Both systems show collective structural change under photoexcitation that ultimately results in a low-symmetry to high-symmetry phase transition. In semimetals, the high symmetry phase relaxes after a few picoseconds, and in manganites, the higher symmetry phase persists essentially indefinitely. A photoinduced structural phase transition in bismuth is discussed in terms of the removal of a Peierls distortion by electronic excitation. When more than 2% of the valence electrons are excited, the Peierls distortion is inverted and the bismuth crystal is collectively driven into a symmetric crystalline phase. An extended two-temperature model is used to interpret and identify a photoinduced symmetric phase that exists above the damage threshold at low temperature and high excitation density. Analogous experiments and analysis on antimony and tellurium are discussed, demonstrating the generality of this method to exploring phase transitions in Peierls-distorted systems. A recently discovered photoinduced insulator-to-metal phase transition in epitaxially strained La2/3Ca1/3MnO3 on an NdGaO3 (001) substrate at low temperature is characterized by frequency-domain and time-domain spectroscopy. The ground state and metastable photoinduced phase in LCMO are characterized by their steady-state behavior. Conventional pump-probe and single-shot experiments are interpreted in terms of an eective medium model that describes the density of charge transfer excitations in the material. An extended two-parameter Ginzburg-Landau model with biquadratic coupling describes the ground state of the manganite phase diagram and the stability of the photoinduced metallic phase.

Photoinduced Phase Transitions Studied by Femtosecond Single-shot Spectroscopy

Photoinduced Phase Transitions Studied by Femtosecond Single-shot Spectroscopy PDF

Author: Taeho Shin

Publisher:

Published: 2010

Total Pages: 228

ISBN-13:

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Single-shot femtosecond spectroscopy has been developed and employed for the study of phase transitions of solid-state materials. Using two crossed echelons, a two dimensional spatial delay gradient was generated across a single probe pulse profile. This novel scheme enables us to monitor irreversible change in solids by acquiring many time-resolved data points with a single laser pulse. With the integration with a non-collinear optical parametric amplifier (NOPA) and a conventional pump-probe instrument, ultrafast dynamics of coherent lattice vibrations and photo-induced phase transitions were examined in two different systems. Ultrafast dynamics such as coherent lattice vibrations and bond softening were investigated for Bi thin films and bulk single crystals. Depending on the thickness, transient reflectivity was changed significantly. The variations are ascribed to different electronic structures possibly originating from quantum confinement. Bond softening exhibits a strong thickness dependence due to hot carrier dynamics as well as to the different electronic structures. At high pump fluences, no phonon oscillations were observed suggesting a phase transition to liquid or to a higher symmetry crystalline phase (reverse Peierls distortion). Together with thermal modeling, double pump measurements reveal nonthermal melting occurring in bulk and thin Bi films. A higher threshold fluence for nonthermal melting is observed in bulk bismuth as compared to thin films, suggesting ultrafast carrier dynamics such as ballistic transport. In addition to nonthermal effects, thermal effects such as inelastic electron-phonon scattering and nonradiative recombination play a crucial role in melting and cooling at later times after nonthermal melting takes place. A quasi one-dimensional platinum iodide complex showed strong oscillations in reflectivity which are attributed to oscillatory motions of wave packets on a selftrapped exciton (STE) potential surface., As optical excitation increased, electron transfer from Pt 2+ to an adjacent Pt4+ occurred over a wider range of lattice sites and weakened the oscillations. Above a certain pump fluence, oscillations disappeared completely indicating that the mixed valence, charge density wave state changed to monovalent, Mott-Hubbard phase. The reverse phase transition, i.e., from the MottHubbard phase to the charge density wave state began within 3 ps of the optical pump.

The Physics of Phase Transitions

The Physics of Phase Transitions PDF

Author: Pierre Papon

Publisher: Springer Science & Business Media

Published: 2013-06-29

Total Pages: 410

ISBN-13: 3662049899

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The Physics of Phase Transitions occupies an important place at the crossroads of several fields central to materials sciences. This second edition incorporates new developments in the states of matter physics, in particular in the domain of nanomaterials and atomic Bose-Einstein condensates where progress is accelerating. New information and application examples are included. This work deals with all classes of phase transitions in fluids and solids, containing chapters on evaporation, melting, solidification, magnetic transitions, critical phenomena, superconductivity, and more. End-of-chapter problems and complete answers are included.

The Photoinduced Phase Transitions of Vanadium Dioxide

The Photoinduced Phase Transitions of Vanadium Dioxide PDF

Author: Kunal Tiwari

Publisher:

Published: 2015

Total Pages:

ISBN-13:

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"The insulator-to-metal transition of vanadium dioxide has attracted the interest of condensed matter physicists for over half a century. In its high-temperature phase, VO2 is metallic with tetragonal rutile crystallography. In its low-temperature phase, it has correlated semiconducting electronic character and a charge-density-wave- like paired monoclinic lattice structure. Determining the relative roles of electron-electron and electron-phonon interactions in the electronic structure of the low temperature phase has been the source of the physics community's interest in VO2.Over the past two decades, it has been shown that the insulator to metal transition may be photoinduced with ultrafast laser pulses. In this thesis we present ultrafast electron diffraction and ultrafast time resolved terahertz spectroscopy measurements of this photoinduced phase transition. Our ultrafast electron diffraction results reveal, at low fluences, a novel metastable phase. This phase has the crystallography of the insulating state, but a dramatically collapsed band gap. A reorganization of valence charge density accompanies this modulated spectroscopic activity.These results have twofold significance. They show that the insulating behavior of the low temperature phase is affected primarily by electron-electron correlations, not by lattice structure. Importantly, they also show that ultrafast electron diffraction may be used to probe both electronic and lattice structure dynamics--it is sensitive to valence charge density reorganizations.Our time resolved terahertz spectroscopy results complement these ultrafast electron diffraction data. We show that, in the novel metastable monoclinic phase, the band gap does not collapse below 50 meV. We also show that dynamics in the time resolved terahertz conductivity through the full photoinduced phase transition occur on two timescales--one fast (240 femtosecond) timescale, characteristic of the coherent athermal photoinduced phase transition; and one slow (picosecond) timescale, characteristic of the astructural transition to the metastable monoclinic phase. In conjunction with our ultrafast electron diffraction measurements, these results suggest that the slow dynamics of the astructural phase transition, and the structural phase transition may be affected by the same underlying mechanism." --

Mechanically Responsive Materials for Soft Robotics

Mechanically Responsive Materials for Soft Robotics PDF

Author: Hideko Koshima

Publisher: John Wiley & Sons

Published: 2020-02-18

Total Pages: 442

ISBN-13: 3527346201

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Offers a comprehensive review of the research and development of mechanically responsive materials and their applications in soft robots Mechanically Responsive Materials for Soft Robotics offers an authoritative guide to the current state of mechanically responsive materials for the development of soft robotics. With contributions from an international panel of experts, the book examines existing mechanically responsive materials such as crystals, polymers, gels, and composites that are stimulated by light and heat. The book also explores the application of mechanical materials to soft robotics. The authors describe the many excellent mechanical crystals developed in recent years that show the ability to bend, twist, rotate, jump, self-heal, and shape memory. Mechanical polymer materials are described for evolution into artificial muscles, photomobile materials, bioinspired soft actuators, inorganic-organic hybrid materials, multi-responsive composite materials, and strain sensor materials. The application of mechanical materials to soft robots is just the beginning. This book reviews the many challenging and versatile applications, such as soft microrobots made from photoresponsive elastomers, four-dimensional printing for assembling soft robots, self-growing of soft robots like plants, and biohybrid robots using muscle tissue. This important book: -Explores recent developments in the use of soft smart materials in robotic systems -Covers the full scope of mechanically responsive materials: polymers, crystals, gels, and nanocomposites -Deals with an interdisciplinary topic of advanced smart materials research -Contains extensive descriptions of current and future applications in soft robotics Written for materials scientists, polymer chemists, photochemists, physical chemists, solid state chemists, inorganic chemists, and robotics engineers, Mechanically Responsive Materials for Soft Robotics offers a comprehensive and timely review of the most recent research on mechanically responsive materials and the manufacture of soft robotics.

Functional Organic Liquids

Functional Organic Liquids PDF

Author: Takashi Nakanishi

Publisher: John Wiley & Sons

Published: 2019-03-12

Total Pages: 323

ISBN-13: 3527804951

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The first book to comprehensively cover the burgeoning new class of soft materials known as functional organic liquids Functional organic liquids, a new concept in soft matter materials science, exhibit favorable properties compared to amorphous polymers and ionic liquids. They are composed of a functional core unit and a side chain, which induces fluidity even at room temperature. Due to their fluidity, functional organic liquids can adopt any shape and geometry and fulfill their function in stretchable and bendable devices for applications in photovoltaics, organic electronics, biomedicine, and biochemistry. Presented in five parts, this book starts with an overview of the design methods and properties of functional organic liquids. The next three parts focus on the applications of this exciting new class of soft materials in the fields of energy conversion, nanotechnology, and biomaterials. They study the liquids for energy conversion, those containing inorganic nanoclusters, and solvent-free soft biomaterials. Functional Organic Liquids concludes with a comparison in terms of properties and application potential between functional organic liquids and more conventional soft matter such as ionic liquids and liquid metals. -Examines the current state of science and technology for functional organic liquids -Focuses on potential and already realized applications such as functional organic liquids for energy conversion -Stimulates researchers to move forward on future development and applications Functional Organic Liquids is an excellent book for materials scientists, polymer chemists, organic chemists, physical chemists, surface chemists, and surface physicists.

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