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Bange JP, Schmitt D, Bennecke W, Meneghini G, AlMutairi A, Watanabe K, Taniguchi T, Steil D, Steil S, Weitz RT, Jansen GSM, Hofmann S, Brem S, Malic E, Reutzel M, Mathias S. Probing electron-hole Coulomb correlations in the exciton landscape of a twisted semiconductor heterostructure. SCIENCE ADVANCES 2024; 10:eadi1323. [PMID: 38324690 PMCID: PMC10849592 DOI: 10.1126/sciadv.adi1323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 01/10/2024] [Indexed: 02/09/2024]
Abstract
In two-dimensional semiconductors, cooperative and correlated interactions determine the material's excitonic properties and can even lead to the creation of correlated states of matter. Here, we study the fundamental two-particle correlated exciton state formed by the Coulomb interaction between single-particle holes and electrons. We find that the ultrafast transfer of an exciton's hole across a type II band-aligned semiconductor heterostructure leads to an unexpected sub-200-femtosecond upshift of the single-particle energy of the electron being photoemitted from the two-particle exciton state. While energy relaxation usually leads to an energetic downshift of the spectroscopic signature, we show that this upshift is a clear fingerprint of the correlated interaction of the electron and hole parts of the exciton. In this way, time-resolved photoelectron spectroscopy is straightforwardly established as a powerful method to access electron-hole correlations and cooperative behavior in quantum materials. Our work highlights this capability and motivates the future study of optically inaccessible correlated excitonic and electronic states of matter.
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Affiliation(s)
- Jan Philipp Bange
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - David Schmitt
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Wiebke Bennecke
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Giuseppe Meneghini
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
| | | | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Daniel Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Sabine Steil
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - R. Thomas Weitz
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany
| | - G. S. Matthijs Jansen
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Stephan Hofmann
- Department of Engineering, University of Cambridge, Cambridge CB3 0FA, UK
| | - Samuel Brem
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Ermin Malic
- Fachbereich Physik, Philipps-Universität Marburg, 35032 Marburg, Germany
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Marcel Reutzel
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
| | - Stefan Mathias
- I. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
- International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, Göttingen, Germany
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Neufeld O, Hübener H, Jotzu G, De Giovannini U, Rubio A. Band Nonlinearity-Enabled Manipulation of Dirac Nodes, Weyl Cones, and Valleytronics with Intense Linearly Polarized Light. NANO LETTERS 2023; 23:7568-7575. [PMID: 37578460 PMCID: PMC10450813 DOI: 10.1021/acs.nanolett.3c02139] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 07/29/2023] [Indexed: 08/15/2023]
Abstract
We study low-frequency linearly polarized laser-dressing in materials with valley (graphene and hexagonal-Boron-Nitride) and topological (Dirac- and Weyl-semimetals) properties. In Dirac-like linearly dispersing bands, the laser substantially moves the Dirac nodes away from their original position, and the movement direction can be fully controlled by rotating the laser polarization. We prove that this effect originates from band nonlinearities away from the Dirac nodes. We further demonstrate that this physical mechanism is widely applicable and can move the positions of the valley minima in hexagonal materials to tune valley selectivity, split and move Weyl cones in higher-order Weyl semimetals, and merge Dirac nodes in three-dimensional Dirac semimetals. The model results are validated with ab initio calculations. Our results directly affect efforts for exploring light-dressed electronic structure, suggesting that one can benefit from band nonlinearity for tailoring material properties, and highlight the importance of the full band structure in nonlinear optical phenomena in solids.
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Affiliation(s)
- Ofer Neufeld
- Center
for Free-electron Laser Science, Max Planck
Institute for the Structure and Dynamics of Matter, Hamburg 22761, Germany
| | - Hannes Hübener
- Center
for Free-electron Laser Science, Max Planck
Institute for the Structure and Dynamics of Matter, Hamburg 22761, Germany
| | - Gregor Jotzu
- Center
for Free-electron Laser Science, Max Planck
Institute for the Structure and Dynamics of Matter, Hamburg 22761, Germany
| | - Umberto De Giovannini
- Center
for Free-electron Laser Science, Max Planck
Institute for the Structure and Dynamics of Matter, Hamburg 22761, Germany
- Dipartimento
di Fisica e Chimica—Emilio Segrè, Università degli Studi di Palermo, Palermo I-90123, Italy
| | - Angel Rubio
- Center
for Free-electron Laser Science, Max Planck
Institute for the Structure and Dynamics of Matter, Hamburg 22761, Germany
- Center
for Computational Quantum Physics (CCQ), The Flatiron Institute, New York, New York 10010, United States
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3
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Formation of moiré interlayer excitons in space and time. Nature 2022; 608:499-503. [PMID: 35978130 DOI: 10.1038/s41586-022-04977-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Accepted: 06/14/2022] [Indexed: 11/09/2022]
Abstract
Moiré superlattices in atomically thin van der Waals heterostructures hold great promise for extended control of electronic and valleytronic lifetimes1-7, the confinement of excitons in artificial moiré lattices8-13 and the formation of exotic quantum phases14-18. Such moiré-induced emergent phenomena are particularly strong for interlayer excitons, where the hole and the electron are localized in different layers of the heterostructure19,20. To exploit the full potential of correlated moiré and exciton physics, a thorough understanding of the ultrafast interlayer exciton formation process and the real-space wavefunction confinement is indispensable. Here we show that femtosecond photoemission momentum microscopy provides quantitative access to these key properties of the moiré interlayer excitons. First, we elucidate that interlayer excitons are dominantly formed through femtosecond exciton-phonon scattering and subsequent charge transfer at the interlayer-hybridized Σ valleys. Second, we show that interlayer excitons exhibit a momentum fingerprint that is a direct hallmark of the superlattice moiré modification. Third, we reconstruct the wavefunction distribution of the electronic part of the exciton and compare the size with the real-space moiré superlattice. Our work provides direct access to interlayer exciton formation dynamics in space and time and reveals opportunities to study correlated moiré and exciton physics for the future realization of exotic quantum phases of matter.
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Heber M, Wind N, Kutnyakhov D, Pressacco F, Arion T, Roth F, Eberhardt W, Rossnagel K. Multispectral time-resolved energy-momentum microscopy using high-harmonic extreme ultraviolet radiation. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022; 93:083905. [PMID: 36050085 DOI: 10.1063/5.0091003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 07/18/2022] [Indexed: 06/15/2023]
Abstract
A 790-nm-driven high-harmonic generation source with a repetition rate of 6 kHz is combined with a toroidal-grating monochromator and a high-detection-efficiency photoelectron time-of-flight momentum microscope to enable time- and momentum-resolved photoemission spectroscopy over a spectral range of 23.6-45.5 eV with sub-100 fs time resolution. Three-dimensional (3D) Fermi surface mapping is demonstrated on graphene-covered Ir(111) with energy and momentum resolutions of ≲100 meV and ≲0.1 Å-1, respectively. The tabletop experiment sets the stage for measuring the kz-dependent ultrafast dynamics of 3D electronic structure, including band structure, Fermi surface, and carrier dynamics in 3D materials as well as 3D orbital dynamics in molecular layers.
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Affiliation(s)
- Michael Heber
- Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - Nils Wind
- Institut für Experimental Physik, Universität Hamburg, 22761 Hamburg, Germany
| | | | | | - Tiberiu Arion
- Centre for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - Friedrich Roth
- Institute of Experimental Physics, TU Bergakademie Freiberg, 09599 Freiberg, Germany
| | - Wolfgang Eberhardt
- Centre for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
| | - Kai Rossnagel
- Ruprecht Haensel Laboratory, Deutsches Elektronen-Synchrotron DESY, 22607 Hamburg, Germany
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Karni O, Esin I, Dani KM. Through the Lens of a Momentum Microscope: Viewing Light-Induced Quantum Phenomena in 2D Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022:e2204120. [PMID: 35817468 DOI: 10.1002/adma.202204120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 06/23/2022] [Indexed: 06/15/2023]
Abstract
Van der Waals (vdW) materials at their 2D limit are diverse, flexible, and unique laboratories to study fundamental quantum phenomena and their future applications. Their novel properties rely on their pronounced Coulomb interactions, variety of crystal symmetries and spin-physics, and the ease of incorporation of different vdW materials to form sophisticated heterostructures. In particular, the excited state properties of many 2D semiconductors and semi-metals are relevant for their technological applications, particularly those that can be induced by light. In this paper, the recent advances made in studying out-of-equilibrium, light-induced, phenomena in these materials are reviewed using powerful, surface-sensitive, time-resolved photoemission-based techniques, with a particular emphasis on the emerging multi-dimensional photoemission spectroscopy technique of time-resolved momentum microscopy. The advances this technique has enabled in studying the nature and dynamics of occupied excited states in these materials are discussed. Then, the future research directions opened by these scientific and instrumental advancements are projected for studying the physics of 2D materials and the opportunities to engineer their band-structure and band-topology by laser fields.
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Affiliation(s)
- Ouri Karni
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
- SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA
| | - Iliya Esin
- Department of Physics, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Keshav M Dani
- Femtosecond Spectroscopy Unit, Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, 904-0495, Japan
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Flavell W. Spiers Memorial Lecture: Prospects for photoelectron spectroscopy. Faraday Discuss 2022; 236:9-57. [DOI: 10.1039/d2fd00071g] [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
An overview is presented of recent advances in photoelectron spectroscopy, focussing on advances in in situ and time-resolved measurements, and in extending the sampling depth of the technique. The future...
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7
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Schönhense G, Medjanik K, Fedchenko O, Zymaková A, Chernov S, Kutnyakhov D, Vasilyev D, Babenkov S, Elmers HJ, Baumgärtel P, Goslawski P, Öhrwall G, Grunske T, Kauerhof T, von Volkmann K, Kallmayer M, Ellguth M, Oelsner A. Time-of-flight photoelectron momentum microscopy with 80-500 MHz photon sources: electron-optical pulse picker or bandpass pre-filter. JOURNAL OF SYNCHROTRON RADIATION 2021; 28:1891-1908. [PMID: 34738944 PMCID: PMC8570213 DOI: 10.1107/s1600577521010511] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 10/10/2021] [Indexed: 06/13/2023]
Abstract
The small time gaps of synchrotron radiation in conventional multi-bunch mode (100-500 MHz) or laser-based sources with high pulse rate (∼80 MHz) are prohibitive for time-of-flight (ToF) based photoelectron spectroscopy. Detectors with time resolution in the 100 ps range yield only 20-100 resolved time slices within the small time gap. Here we present two techniques of implementing efficient ToF recording at sources with high repetition rate. A fast electron-optical beam blanking unit with GHz bandwidth, integrated in a photoelectron momentum microscope, allows electron-optical `pulse-picking' with any desired repetition period. Aberration-free momentum distributions have been recorded at reduced pulse periods of 5 MHz (at MAX II) and 1.25 MHz (at BESSY II). The approach is compared with two alternative solutions: a bandpass pre-filter (here a hemispherical analyzer) or a parasitic four-bunch island-orbit pulse train, coexisting with the multi-bunch pattern on the main orbit. Chopping in the time domain or bandpass pre-selection in the energy domain can both enable efficient ToF spectroscopy and photoelectron momentum microscopy at 100-500 MHz synchrotrons, highly repetitive lasers or cavity-enhanced high-harmonic sources. The high photon flux of a UV-laser (80 MHz, <1 meV bandwidth) facilitates momentum microscopy with an energy resolution of 4.2 meV and an analyzed region-of-interest (ROI) down to <800 nm. In this novel approach to `sub-µm-ARPES' the ROI is defined by a small field aperture in an intermediate Gaussian image, regardless of the size of the photon spot.
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Affiliation(s)
- G. Schönhense
- Institut für Physik, Johannes Gutenberg Universität, 55128 Mainz, Germany
| | - K. Medjanik
- Institut für Physik, Johannes Gutenberg Universität, 55128 Mainz, Germany
| | - O. Fedchenko
- Institut für Physik, Johannes Gutenberg Universität, 55128 Mainz, Germany
| | - A. Zymaková
- Institut für Physik, Johannes Gutenberg Universität, 55128 Mainz, Germany
| | - S. Chernov
- Institut für Physik, Johannes Gutenberg Universität, 55128 Mainz, Germany
| | - D. Kutnyakhov
- Institut für Physik, Johannes Gutenberg Universität, 55128 Mainz, Germany
| | - D. Vasilyev
- Institut für Physik, Johannes Gutenberg Universität, 55128 Mainz, Germany
| | - S. Babenkov
- Institut für Physik, Johannes Gutenberg Universität, 55128 Mainz, Germany
| | - H. J. Elmers
- Institut für Physik, Johannes Gutenberg Universität, 55128 Mainz, Germany
| | | | - P. Goslawski
- BESSY II, Helmholtz-Zentrum, 12489 Berlin, Germany
| | - G. Öhrwall
- MAX IV Laboratory, Lund University, PO Box 118, SE-221 00 Lund, Sweden
| | | | | | | | | | - M. Ellguth
- Surface Concept GmbH, 55128 Mainz, Germany
| | - A. Oelsner
- Surface Concept GmbH, 55128 Mainz, Germany
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