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Richter S, Rebarz M, Herrfurth O, Espinoza S, Schmidt-Grund R, Andreasson J. Broadband femtosecond spectroscopic ellipsometry. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:033104. [PMID: 33820054 DOI: 10.1063/5.0027219] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 01/31/2021] [Indexed: 06/12/2023]
Abstract
We present a setup for time-resolved spectroscopic ellipsometry in a pump-probe scheme using femtosecond laser pulses. As a probe, the system deploys supercontinuum white light pulses that are delayed with respect to single-wavelength pump pulses. A polarizer-sample-compensator-analyzer configuration allows ellipsometric measurements by scanning the compensator azimuthal angle. The transient ellipsometric parameters are obtained from a series of reflectance-difference spectra that are measured for various pump-probe delays and polarization (compensator) settings. The setup is capable of performing time-resolved spectroscopic ellipsometry from the near-infrared through the visible to the near-ultraviolet spectral range at 1.3 eV-3.6 eV. The temporal resolution is on the order of 100 fs within a delay range of more than 5 ns. We analyze and discuss critical aspects such as fluctuations of the probe pulses and imperfections of the polarization optics and present strategies deployed for circumventing related issues.
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Affiliation(s)
- Steffen Richter
- ELI Beamlines/Fyzikální ústav AV ČR, v.v.i., Za Radnicí 835, 25241 Dolní Břežany, Czech Republic
| | - Mateusz Rebarz
- ELI Beamlines/Fyzikální ústav AV ČR, v.v.i., Za Radnicí 835, 25241 Dolní Břežany, Czech Republic
| | - Oliver Herrfurth
- Universität Leipzig, Felix-Bloch-Institut für Festkörperphysik, Linnéstr. 5, 04103 Leipzig, Germany
| | - Shirly Espinoza
- ELI Beamlines/Fyzikální ústav AV ČR, v.v.i., Za Radnicí 835, 25241 Dolní Břežany, Czech Republic
| | - Rüdiger Schmidt-Grund
- Universität Leipzig, Felix-Bloch-Institut für Festkörperphysik, Linnéstr. 5, 04103 Leipzig, Germany
| | - Jakob Andreasson
- ELI Beamlines/Fyzikální ústav AV ČR, v.v.i., Za Radnicí 835, 25241 Dolní Břežany, Czech Republic
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Montanaro A, Giusti F, Colja M, Brajnik G, Marciniak AMA, Sergo R, De Angelis D, Glerean F, Sparapassi G, Jarc G, Carrato S, Cautero G, Fausti D. Visible pump-mid infrared pump-broadband probe: Development and characterization of a three-pulse setup for single-shot ultrafast spectroscopy at 50 kHz. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:073106. [PMID: 32752873 DOI: 10.1063/5.0016362] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 06/22/2020] [Indexed: 06/11/2023]
Abstract
We report here an experimental setup to perform three-pulse pump-probe measurements over a wide wavelength and temperature range. By combining two pump pulses in the visible (650 nm-900 nm) and mid-IR (5 μm-20 μm) range, with a broadband supercontinuum white-light probe, our apparatus enables both the combined selective excitation of different material degrees of freedom and a full time-dependent reconstruction of the non-equilibrium dielectric function of the sample. We describe here the optical setup, the cryogenic sample environment, and the custom-made acquisition electronics capable of referenced single-pulse detection of broadband spectra at the maximum repetition rate of 50 kHz, achieving a sensitivity of the order of 10-4 over an integration time of 1 s. We demonstrate the performance of the setup by reporting data on a mid-IR pump, optical push, and broadband probe in a single crystal of Bi2Sr2Y0.08Ca0.92Cu2O8+δ across the superconducting and pseudogap phases.
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Affiliation(s)
- Angela Montanaro
- Department of Physics, Università degli Studi di Trieste, 34127 Trieste, Italy
| | - Francesca Giusti
- Department of Physics, Università degli Studi di Trieste, 34127 Trieste, Italy
| | - Matija Colja
- Elettra Sincrotrone Trieste S.C.p.A., 34127 Basovizza Trieste, Italy
| | - Gabriele Brajnik
- Elettra Sincrotrone Trieste S.C.p.A., 34127 Basovizza Trieste, Italy
| | | | - Rudi Sergo
- Elettra Sincrotrone Trieste S.C.p.A., 34127 Basovizza Trieste, Italy
| | - Dario De Angelis
- Elettra Sincrotrone Trieste S.C.p.A., 34127 Basovizza Trieste, Italy
| | - Filippo Glerean
- Department of Physics, Università degli Studi di Trieste, 34127 Trieste, Italy
| | - Giorgia Sparapassi
- Department of Physics, Università degli Studi di Trieste, 34127 Trieste, Italy
| | - Giacomo Jarc
- Department of Physics, Università degli Studi di Trieste, 34127 Trieste, Italy
| | - Sergio Carrato
- Department of Engineering and Architecture, Università degli Studi di Trieste, 34127 Trieste, Italy
| | - Giuseppe Cautero
- Elettra Sincrotrone Trieste S.C.p.A., 34127 Basovizza Trieste, Italy
| | - Daniele Fausti
- Department of Physics, Università degli Studi di Trieste, 34127 Trieste, Italy
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Abstract
The role of the crystal lattice for the electronic properties of cuprates and other high-temperature superconductors remains controversial despite decades of theoretical and experimental efforts. While the paradigm of strong electronic correlations suggests a purely electronic mechanism behind the insulator-to-metal transition, recently the mutual enhancement of the electron-electron and the electron-phonon interaction and its relevance to the formation of the ordered phases have also been emphasized. Here, we combine polarization-resolved ultrafast optical spectroscopy and state-of-the-art dynamical mean-field theory to show the importance of the crystal lattice in the breakdown of the correlated insulating state in an archetypal undoped cuprate. We identify signatures of electron-phonon coupling to specific fully symmetric optical modes during the buildup of a three-dimensional (3D) metallic state that follows charge photodoping. Calculations for coherently displaced crystal structures along the relevant phonon coordinates indicate that the insulating state is remarkably unstable toward metallization despite the seemingly large charge-transfer energy scale. This hitherto unobserved insulator-to-metal transition mediated by fully symmetric lattice modes can find extensive application in a plethora of correlated solids.
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Palmieri T, Baldini E, Steinhoff A, Akrap A, Kollár M, Horváth E, Forró L, Jahnke F, Chergui M. Mahan excitons in room-temperature methylammonium lead bromide perovskites. Nat Commun 2020; 11:850. [PMID: 32051405 PMCID: PMC7016123 DOI: 10.1038/s41467-020-14683-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2019] [Accepted: 01/21/2020] [Indexed: 11/09/2022] Open
Abstract
In a seminal paper, Mahan predicted that excitonic bound states can still exist in a semiconductor at electron-hole densities above the insulator-to-metal Mott transition. However, no clear evidence for this exotic quasiparticle, dubbed Mahan exciton, exists to date at room temperature. In this work, we combine ultrafast broadband optical spectroscopy and advanced many-body calculations to reveal that organic-inorganic lead-bromide perovskites host Mahan excitons at room temperature. Persistence of the Wannier exciton peak and the enhancement of the above-bandgap absorption are observed at all achievable photoexcitation densities, well above the Mott density. This is supported by the solution of the semiconductor Bloch equations, which confirms that no sharp transition between the insulating and conductive phase occurs. Our results demonstrate the robustness of the bound states in a regime where exciton dissociation is otherwise expected, and offer promising perspectives in fundamental physics and in room-temperature applications involving high densities of charge carriers.
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Affiliation(s)
- Tania Palmieri
- Laboratory of Ultrafast Spectroscopy, Lausanne Centre for Ultrafast Science (LACUS), Institute of Chemistry and Chemical Engineering (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Edoardo Baldini
- Laboratory of Ultrafast Spectroscopy, Lausanne Centre for Ultrafast Science (LACUS), Institute of Chemistry and Chemical Engineering (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
| | - Alexander Steinhoff
- Semiconductor Theory Group, Institute for Theoretical Physics, University of Bremen, Otto-Hahn-Alle 1, P.O. Box 330440, Bremen, Germany
| | - Ana Akrap
- Group of Light Fermion Spectroscopy, Department of Physics, Université de Fribourg, 3 Chemin du Musée, 1700, Fribourg, Switzerland
| | - Márton Kollár
- Laboratory of Physics of Condensed Matter, Institute of Physics (IPHYS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Endre Horváth
- Laboratory of Physics of Condensed Matter, Institute of Physics (IPHYS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - László Forró
- Laboratory of Physics of Condensed Matter, Institute of Physics (IPHYS), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland
| | - Frank Jahnke
- Semiconductor Theory Group, Institute for Theoretical Physics, University of Bremen, Otto-Hahn-Alle 1, P.O. Box 330440, Bremen, Germany
| | - Majed Chergui
- Laboratory of Ultrafast Spectroscopy, Lausanne Centre for Ultrafast Science (LACUS), Institute of Chemistry and Chemical Engineering (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
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Baldini E, Mann A, Benfatto L, Cappelluti E, Acocella A, Silkin VM, Eremeev SV, Kuzmenko AB, Borroni S, Tan T, Xi XX, Zerbetto F, Merlin R, Carbone F. Real-Time Observation of Phonon-Mediated σ-π Interband Scattering in MgB_{2}. PHYSICAL REVIEW LETTERS 2017; 119:097002. [PMID: 28949564 DOI: 10.1103/physrevlett.119.097002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Indexed: 06/07/2023]
Abstract
In systems having an anisotropic electronic structure, such as the layered materials graphite, graphene, and cuprates, impulsive light excitation can coherently stimulate specific bosonic modes, with exotic consequences for the emergent electronic properties. Here we show that the population of E_{2g} phonons in the multiband superconductor MgB_{2} can be selectively enhanced by femtosecond laser pulses, leading to a transient control of the number of carriers in the σ-electronic subsystem. The nonequilibrium evolution of the material optical constants is followed in the spectral region sensitive to both the a- and c-axis plasma frequencies and modeled theoretically, revealing the details of the σ-π interband scattering mechanism in MgB_{2}.
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Affiliation(s)
- E Baldini
- Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
- Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - A Mann
- Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - L Benfatto
- Institute for Complex Systems-CNR, and Physics Department, University of Rome "La Sapienza", I-00185 Rome, Italy
| | - E Cappelluti
- Institute for Complex Systems-CNR, and Physics Department, University of Rome "La Sapienza", I-00185 Rome, Italy
| | - A Acocella
- Department of Chemistry "G. Ciamician," Università di Bologna, I-40126 Bologna, Italy
| | - V M Silkin
- Departamento de Física de Materiales, Universidad del País Vasco, 20080 San Sebastián/Donostia, Spain
- Donostia International Physics Center, 20018 San Sebastián/Donostia, Spain
- IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain
| | - S V Eremeev
- Institute of Strength Physics and Materials Science, 634055 Tomsk, Russia
- Tomsk State University, 634050 , Tomsk, Russia
| | - A B Kuzmenko
- Department of Quantum Matter Physics, University of Geneva, CH-1211 Geneva 4, Switzerland
| | - S Borroni
- Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - T Tan
- Department of Material Science and Engineering, The Pennsylvania State University, Pennsylvania 16802, USA
| | - X X Xi
- Department of Material Science and Engineering, The Pennsylvania State University, Pennsylvania 16802, USA
| | - F Zerbetto
- Department of Chemistry "G. Ciamician," Università di Bologna, I-40126 Bologna, Italy
| | - R Merlin
- Department of Physics, Center for Photonics and Multiscale Nanomaterials, University of Michigan, Ann Arbor, Michigan 48109-1040, USA
| | - F Carbone
- Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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