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Caprini L, Löwen H, Geilhufe RM. Ultrafast entropy production in pump-probe experiments. Nat Commun 2024; 15:94. [PMID: 38169471 PMCID: PMC10761836 DOI: 10.1038/s41467-023-44277-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 12/06/2023] [Indexed: 01/05/2024] Open
Abstract
The ultrafast control of materials has opened the possibility to investigate non-equilibrium states of matter with striking properties, such as transient superconductivity and ferroelectricity, ultrafast magnetization and demagnetization, as well as Floquet engineering. The characterization of the ultrafast thermodynamic properties within the material is key for their control and design. Here, we develop the ultrafast stochastic thermodynamics for laser-excited phonons. We calculate the entropy production and heat absorbed from experimental data for single phonon modes of driven materials from time-resolved X-ray scattering experiments where the crystal is excited by a laser pulse. The spectral entropy production is calculated for SrTiO3 and KTaO3 for different temperatures and reveals a striking relation with the power spectrum of the displacement-displacement correlation function by inducing a broad peak beside the eigenmode-resonance.
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Affiliation(s)
- Lorenzo Caprini
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, 40225, Düsseldorf, Germany.
| | - Hartmut Löwen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, 40225, Düsseldorf, Germany
| | - R Matthias Geilhufe
- Department of Physics, Chalmers University of Technology, 412 96, Göteborg, Sweden.
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Nakamura K, Tanimura Y. Optical response of laser-driven charge-transfer complex described by Holstein-Hubbard model coupled to heat baths: Hierarchical equations of motion approach. J Chem Phys 2021; 155:064106. [PMID: 34391366 DOI: 10.1063/5.0060208] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the optical response of a charge-transfer complex in a condensed phase driven by an external laser field. Our model includes an instantaneous short-range Coulomb interaction and a local optical vibrational mode described by the Holstein-Hubbard (HH) model. Although characterization of the HH model for a bulk system has typically been conducted using a complex phase diagram, this approach is not sufficient for investigations of dynamical behavior at finite temperature, in particular for studies of nonlinear optical properties, where the time irreversibility of the dynamics that arises from the environment becomes significant. We therefore include heat baths with infinite heat capacity in the model to introduce thermal effects characterized by fluctuation and dissipation to the system dynamics. By reducing the number of degrees of freedom of the heat baths, we derive numerically "exact" hierarchical equations of motion for the reduced density matrix of the HH system. As demonstrations, we calculate the optical response of the system in two- and four-site cases under external electric fields. The results indicate that the effective strength of the system-bath coupling becomes large as the number of sites increases. Excitation of electrons promotes the conductivity when the Coulomb repulsion is equivalent to or dominates the electron-phonon coupling, whereas excitation of optical vibrations always suppresses the conductivity.
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Affiliation(s)
- Kiyoto Nakamura
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyoku, Kyoto 606-8502, Japan
| | - Yoshitaka Tanimura
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyoku, Kyoto 606-8502, Japan
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Juraschek DM, Narang P. Highly Confined Phonon Polaritons in Monolayers of Perovskite Oxides. NANO LETTERS 2021; 21:5098-5104. [PMID: 34101474 DOI: 10.1021/acs.nanolett.1c01002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Two-dimensional (2D) materials are able to strongly confine light hybridized with collective excitations of atoms, enabling electric-field enhancements and novel spectroscopic applications. Recently, freestanding monolayers of perovskite oxides have been synthesized, which possess highly infrared-active phonon modes and a complex interplay of competing interactions. Here, we show that this new class of 2D materials exhibits highly confined phonon polaritons by evaluating central figures of merit for phonon polaritons in the tetragonal phases of the 2D perovskites SrTiO3, KTaO3, and LiNbO3, using density functional theory calculations. Specifically, we compute the 2D phonon-polariton dispersions, the propagation-quality, confinement, and deceleration factors, and we show that they are comparable to those found in the prototypical 2D dielectric hexagonal boron nitride. Our results suggest that monolayers of perovskite oxides are promising candidates for polaritonic platforms that enable new possibilities in terms of tunability and spectral ranges.
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Affiliation(s)
- Dominik M Juraschek
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Prineha Narang
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States
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Buzzi M, Först M, Cavalleri A. Measuring non-equilibrium dynamics in complex solids with ultrashort X-ray pulses. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2019; 377:20170478. [PMID: 30929635 PMCID: PMC6452049 DOI: 10.1098/rsta.2017.0478] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Strong interactions between electrons give rise to the complexity of quantum materials, which exhibit exotic functional properties and extreme susceptibility to external perturbations. A growing research trend involves the study of these materials away from equilibrium, especially in cases in which the stimulation with optical pulses can coherently enhance cooperative orders. Time-resolved X-ray probes are integral to this type of research, as they can be used to track atomic and electronic structures as they evolve on ultrafast timescales. Here, we review a series of recent experiments where femtosecond X-ray diffraction was used to measure dynamics of complex solids. This article is part of the theme issue 'Measurement of ultrafast electronic and structural dynamics with X-rays'.
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Affiliation(s)
- Michele Buzzi
- Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany
| | - Michael Först
- Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany
| | - Andrea Cavalleri
- Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany
- Department of Physics, Oxford University, Clarendon Laboratory, Oxford, UK
- e-mail:
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Abstract
We use coherent midinfrared optical pulses to resonantly excite large-amplitude oscillations of the Si-C stretching mode in silicon carbide. When probing the sample with a second pulse, we observe parametric optical gain at all wavelengths throughout the reststrahlen band. This effect reflects the amplification of light by phonon-mediated four-wave mixing and, by extension, of optical-phonon fluctuations. Density functional theory calculations clarify aspects of the microscopic mechanism for this phenomenon. The high-frequency dielectric permittivity and the phonon oscillator strength depend quadratically on the lattice coordinate; they oscillate at twice the frequency of the optical field and provide a parametric drive for the lattice mode. Parametric gain in phononic four-wave mixing is a generic mechanism that can be extended to all polar modes of solids, as a means to control the kinetics of phase transitions, to amplify many-body interactions or to control phonon-polariton waves.
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Pontius N, Beye M, Trabant C, Mitzner R, Sorgenfrei F, Kachel T, Wöstmann M, Roling S, Zacharias H, Ivanov R, Treusch R, Buchholz M, Metcalf P, Schüßler-Langeheine C, Föhlisch A. Probing the non-equilibrium transient state in magnetite by a jitter-free two-color X-ray pump and X-ray probe experiment. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2018; 5:054501. [PMID: 30310825 PMCID: PMC6158032 DOI: 10.1063/1.5042847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 08/23/2018] [Indexed: 06/08/2023]
Abstract
We present a general experimental concept for jitter-free pump and probe experiments at free electron lasers. By generating pump and probe pulse from one and the same X-ray pulse using an optical split-and-delay unit, we obtain a temporal resolution that is limited only by the X-ray pulse lengths. In a two-color X-ray pump and X-ray probe experiment with sub 70 fs temporal resolution, we selectively probe the response of orbital and charge degree of freedom in the prototypical functional oxide magnetite after photoexcitation. We find electronic order to be quenched on a time scale of (30 ± 30) fs and hence most likely faster than what is to be expected for any lattice dynamics. Our experimental result hints to the formation of a short lived transient state with decoupled electronic and lattice degree of freedom in magnetite. The excitation and relaxation mechanism for X-ray pumping is discussed within a simple model leading to the conclusion that within the first 10 fs the original photoexcitation decays into low-energy electronic excitations comparable to what is achieved by optical pump pulse excitation. Our findings show on which time scales dynamical decoupling of degrees of freedom in functional oxides can be expected and how to probe this selectively with soft X-ray pulses. Results can be expected to provide crucial information for theories for ultrafast behavior of materials and help to develop concepts for novel switching devices.
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Affiliation(s)
- N Pontius
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - M Beye
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - C Trabant
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - R Mitzner
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - F Sorgenfrei
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - T Kachel
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - M Wöstmann
- WWU Münster, Physikalisches Institut, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
| | - S Roling
- WWU Münster, Physikalisches Institut, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
| | - H Zacharias
- WWU Münster, Physikalisches Institut, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany
| | - R Ivanov
- Deutsches Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg, Germany
| | - R Treusch
- Deutsches Elektronen-Synchrotron, Notkestr. 85, 22607 Hamburg, Germany
| | - M Buchholz
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
| | - P Metcalf
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - C Schüßler-Langeheine
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany
| | - A Föhlisch
- Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany
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