Article
Materials Science, Multidisciplinary
A. Ino, T. Kubo, S. Ishizaka, H. Takita, W. Mansuer, K. Shimada, S. Ueda, H. Kito, I Hase, S. Ishida, K. Oka, H. Fujihisa, Y. Gotoh, Y. Yoshida, A. Iyo, H. Ogino, H. Eisaki, K. Kawashima, Y. Yanagi
Summary: This study reports the direct observation of the electronic structure of the phosphide superconductor ZrP2-xSex using high-resolution bulk-sensitive hard x-ray photoemission spectroscopy. It reveals that the valence charges of P atoms at different crystallographic sites are different and their occupation ratio varies with x. The findings also suggest that the electronic states at the Fermi level are mainly attributed to the Zr 4d band and replacing Se2- with P3- serves as hole doping.
Article
Chemistry, Multidisciplinary
Michele Pugini, Bruno Credidio, Irina Walter, Sebastian Malerz, Florian Trinter, Dominik Stemer, Uwe Hergenhahn, Gerard Meijer, Iain Wilkinson, Bernd Winter, Stephan Thurmer
Summary: The recent application of concepts from condensed-matter physics to photoelectron spectroscopy of liquid-phase systems enables the measurement of electronic energetics of liquids on an absolute scale. The authors connect the newly accessible energy level to the solution work function and demonstrate accurate measurements of concentration-dependent work functions in aqueous solutions under controlled conditions. This work marks the beginning of a new era in the characterization of the interfacial electronic structure of aqueous solutions and liquids more generally.
Article
Chemistry, Multidisciplinary
Michele Pugini, Bruno Credidio, Irina Walter, Sebastian Malerz, Florian Trinter, Dominik Stemer, Uwe Hergenhahn, Gerard Meijer, Iain Wilkinson, Bernd Winter, Stephan Thurmer
Summary: The recent application of condensed-matter physics concepts to photoelectron spectroscopy (PES) of liquid-phase systems has allowed for the measurement of electronic energetics of liquids. The vertical ionization energies (VIEs) of liquid water and aqueous solutions can now be accurately determined and referenced to the local vacuum level. This work discusses the connection between these energies and the solution work function and demonstrates the accurate measurement of concentration-dependent work functions for an aqueous solution.
Article
Nanoscience & Nanotechnology
Melanie A. Jenkins, Konner E. K. Holden, Sean W. Smith, Michael T. Brumbach, M. David Henry, Conan Weiland, Joseph C. Woicik, Samantha T. Jaszewski, Jon F. Ihlefeld, John F. Conley
Summary: In this study, energy barriers between various metal electrodes and doped ferroelectric HfO2 were directly measured using internal photoemission (IPE) spectroscopy, and the results were compared with valence band offsets determined by X-ray photoelectron spectroscopy (XPS) and hard X-ray photoelectron spectroscopy (HAXPES). Both XPS and IPE methods showed similar dependence of the HfO2 barrier on metal work function. However, barrier heights determined by XPS and HAXPES were on average about 1.1 eV smaller than those determined by IPE, indicating the presence of negative charge in the HfO2.
ACS APPLIED MATERIALS & INTERFACES
(2021)
Article
Materials Science, Multidisciplinary
Jiri Volny, Katerina Charvatova, Martin Veis, Vaclav Holy, Martin Vondracek, Jan Honolka, Elen Duverger-Nedellec, Jakub Schusser, Sunil W. D'Souza, Jan Minar, James M. Pientka, Alberto Marmodoro, Karel Vyborny, Klara Uhlirova
Summary: The synthesis of single-crystalline NaMnAs and its high-quality confirmation by x-ray photoemission spectra are reported. Magnetometry results confirm the antiferromagnetic order. The optical transmittance measurements and theoretical modeling using LDA+U support the prediction of NaMnAs as a semiconductor. The Neel temperature determination from susceptibility-temperature dependence agrees with Monte Carlo simulations.
Article
Materials Science, Multidisciplinary
J. G. Tobin, H. Ramanantoanina, C. Daul, P. Roussel, S-W Yu, S. Nowak, R. Alonso-Mori, T. Kroll, D. Nordlund, T-C Weng, D. Sokaras
Summary: Ligand field density functional theory calculations and high-energy-resolution fluorescence detection combined with inverse photoelectron spectroscopy measurements were used to study the 5f electronic structure of the dioxides of thorium, uranium, and plutonium, providing insight into their unoccupied states.
Article
Physics, Multidisciplinary
Yue Qiao, Jun Wang, Yan Yan, Simeng Song, Zhou Chen, Aihua Liu, Jigen Chen, Fuming Guo, Yujun Yang
Summary: In this study, high-order harmonic generation (HHG) from an atom illuminated by a sinusoidally phase-modulated pulse is investigated using the time-dependent Schrodinger equation. The results show that the photon energy of the generated harmonics can be controlled by adjusting the phase parameters, resulting in spectral shift.
Article
Chemistry, Inorganic & Nuclear
Paul S. Bagus, Connie J. Nelin, C. Richard Brundle, B. Vincent Crist, Eugene S. Ilton, Nabajit Lahiri, Kevin M. Rosso
Summary: The origin and assignment of the complex main and satellite X-ray photoelectron spectroscopy (XPS) features of the cations in ionic compounds have been the subject of extensive theoretical studies. Different configurations need to be considered when analyzing XPS features, and the use of optimized orbitals can help in accurately describing the contributions of different ionic configurations to the full XPS spectra. The molecular orbital methods used in this work provide insights into the electronic structure of the material and help in definitively assigning the character and origin of main and satellite XPS features.
INORGANIC CHEMISTRY
(2022)
Article
Chemistry, Physical
Stefania Baronio, Valeria De Leo, Ginevra Lautizi, Paola Mantegazza, Eleonora Natale, Manuel Tuniz, Stefano Vigneri, Luca Bignardi, Paolo Lacovig, Silvano Lizzit, Alessandro Baraldi
Summary: The vibrational features of carbon monoxide (CO) adsorbed on Ir(111) surface were studied using high-resolution core-level spectroscopy, confirming that CO always adsorbs on the surface in on-top sites. Measurements of C 1s vibrational splittings for different structures were in agreement with the Z + 1 model. Despite very small measurement errors, any anharmonic contribution to the spectral lineshape could not be identified.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Physical
Stefania Baronio, Valeria De Leo, Ginevra Lautizi, Paola Mantegazza, Eleonora Natale, Manuel Tuniz, Stefano Vigneri, Luca Bignardi, Paolo Lacovig, Silvano Lizzit, Alessandro Baraldi
Summary: The vibrational features of carbon monoxide adsorbed on Ir(111) surface were studied using high-resolution core-level spectroscopy, indicating CO always adsorbs in on-top sites. The C 1s vibrational splittings measured were in good agreement with the Z + 1 model, but no anharmonic contribution was observed in the spectral lineshape.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Physics, Applied
Sophia Sahoo, Anupam Jana, Satish Yadav, Rajeev Rawat, D. M. Phase, R. J. Choudhary
Summary: Exploring the electronic parameters contributing to the external control of conductivity of correlated systems like V2O3 is important for next-generation Mottronic devices. In this study, a resistive-switching phenomenon from the high-resistance state (HRS) to the low-resistance state is demonstrated in a V2O3 thin film by applying a dc voltage. The study reveals an electrically induced nonthermal resistive-switching effect in the V2O3 thin film.
PHYSICAL REVIEW APPLIED
(2023)
Article
Chemistry, Multidisciplinary
Stephan Thurmer, Sebastian Malerz, Florian Trinter, Uwe Hergenhahn, Chin Lee, Daniel M. Neumark, Gerard Meijer, Bernd Winter, Iain Wilkinson
Summary: The study demonstrates a new method to accurately determine the electronic energetics of liquid water and aqueous solutions, including vertical ionization energies of water solvent and solute on an absolute chemical potential scale. By implementing innovative techniques, researchers successfully determined the VIE and oxidative stability of liquid water, and revealed the contraction of the solution's work function.
Article
Chemistry, Physical
Jin-Kun Zeng, Huai-Qian Wang, Hui-Fang Li, Biao Xie, Long-Ying Jiang, Jia-Ming Zhang, Lan-Xin Qin
Summary: The structural evolution, electronic property and spectral analysis of YGenq (n = 4-20, q = 0, -1) have been investigated using density functional theory combined with the Artificial Bees Colony and the Saunders 'Kick' algorithm. The global minimum structure of YGen- cluster is determined by comparing simulated and measured photoelectron spectra (PES). Changes in average binding energies, second difference energies, and highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps show abnormal stability at n = 16. Charge transfer from Ge to Y atom is observed in YGe16- through natural population analysis (NPA), indicating ionic bonding. HOMO-LUMO orbitals are predominantly composed of Ge atoms. Electron localisation function (ELF) reveals electrostatic forces between Y and Ge atoms and covalent interactions among Ge atoms, consistent with bond analysis. YGe16- is identified as a promising building block for rare earth-doped semiconductor materials.
Article
Biochemical Research Methods
Babita Bisht, Priyank Bhardwaj, Manoj Giri, Sanjay Pant
Summary: Methyl orange, an azo dye, exhibits strong fluorescence properties in different solvents, with fluorescence quantum yield dependent on the solvent and solute-solvent interaction affecting the fluorescence spectra significantly.
JOURNAL OF FLUORESCENCE
(2021)
Article
Chemistry, Multidisciplinary
R. Castrillo-Bodero, M. Blanco-Rey, K. Ali, J. E. Ortega, F. Schiller, L. Fernandez
Summary: Magnetic hybrid metal-organic interfaces have great potential in areas such as organic spintronics and quantum information processing. However, it is crucial to be able to tune the carrier injection barriers on-demand for technological devices. In this study, we prepared hybrid metal-organic interfaces by adsorbing copper phthalocyanine CuPc on REAu2 surfaces and investigated their growth, electrostatics, and electronic structure. Our results showed that the RE valence of the substrate has a significant effect on the carrier injection barrier of the interface.
Article
Physics, Applied
Fatemeh Chahshouri, Masoud Taleb, Florian K. Diekmann, Kai Rossnagel, Nahid Talebi
Summary: This study reports on the effect of electron-beam deceleration on Cherenkov radiation in nm-thick WSe2 crystals and investigates the interaction between excitons and generated photons beyond the non-recoil approximation.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
Yingchao Zhang, Xun Shi, Mengxue Guan, Wenjing You, Yigui Zhong, Tika R. Kafle, Yaobo Huang, Hong Ding, Michael Bauer, Kai Rossnagel, Sheng Meng, Henry C. Kapteyn, Margaret M. Murnane
Summary: In this study, a novel inverted CDW state was discovered in 1T-TaSe2 by using a femtosecond laser to manipulate charge-lattice orders and couplings. The unique properties of this state, such as increased density of states, high metallicity, and altered electron-phonon couplings, were revealed through time- and angle-resolved photoemission spectroscopy and time-dependent density functional theory.
STRUCTURAL DYNAMICS-US
(2022)
Article
Materials Science, Multidisciplinary
Antonio Sanna, Camilla Pellegrini, Eva Liebhaber, Kai Rossnagel, Katharina J. Franke, E. K. U. Gross
Summary: We performed an STM and ab-initio study on the anisotropic superconductivity of 2H-NbSe2 in the CDW phase. Our results show a clear double-peak structure in the differential-conductance spectra, and the density functional theory simulations accurately reproduce the observed superconducting gap. We identified the high-gap region responsible for the main STM peak as the CC layer, which belongs to the same Fermi surface sheet broken by the CDW gap opening. Our findings suggest a spatially localized competition between superconductivity and CDW in the HC regions of the crystal.
NPJ QUANTUM MATERIALS
(2022)
Article
Multidisciplinary Sciences
Eva Liebhaber, Lisa M. Ruetten, Gael Reecht, Jacob F. Steiner, Sebastian Rohlf, Kai Rossnagel, Felix von Oppen, Katharina J. Franke
Summary: In this study, the authors used scanning tunnelling microscopy to investigate the excitation spectra of Fe chains on a NbSe2 surface, focusing on the regime of quantum spins. They found fascinating features of the magnetic adatom chains, such as quantum phase transition, hybridization, and band formation of the excitations. This study provides insights into the correlated-electron physics and its interplay with topological superconductivity.
NATURE COMMUNICATIONS
(2022)
Article
Chemistry, Inorganic & Nuclear
A. Roychowdhury, T. K. Dalui, P. K. Ghose, S. K. Mahatha, N. Wind, K. Rossnagel, S. Majumdar, S. Giri
Summary: The study reports magnetoresistance and magnetization properties of single-crystal GaGeTe, demonstrating its unique electrical and magnetic characteristics. Hall measurements indicate p-type conductivity, while angle-resolved photoemission spectroscopy confirms the peculiar dispersion shape of the valence band.
JOURNAL OF SOLID STATE CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Chao Li, Roberto Robles, Nicolas Lorente, Sanjoy Kr Mahatha, Sebastian Rohlf, Kai Rossnagel, Alessandro Barla, Boris V. Sorokin, Stefano Rusponi, Philippe Ohresser, Sara Realista, Paulo N. Martinho, Torben Jasper-Toennies, Alexander Weismann, Richard Berndt, Manuel Gruber
Summary: The magnetic properties of transition-metal ions are usually described by atomic spins and exchange coupling, with the orbital moment seen as a perturbation. However, our study on a Co-(II) complex with antiferromagnetically coupled 1/2 spins on Au(111) reveals that each Co ion has a comparable orbital moment to the spin, leading to magnetic anisotropy. This finding emphasizes the importance of considering orbital moments, even in systems with strong ligand fields, and has important consequences for quantum operations.
Article
Physics, Multidisciplinary
Masoud Taleb, Mario Hentschel, Kai Rossnagel, Harald Giessen, Nahid Talebi
Summary: Ultrafast photon-electron spectroscopy in electron microscopes commonly requires ultrafast laser setups. Now, an inverse approach based on cathodoluminescence spectroscopy has allowed a compact solution to spectral interferometry inside an electron microscope, without a laser.
Article
Physics, Multidisciplinary
Tobias Heinrich, Hung-Tzu Chang, Sergey Zayko, Kai Rossnagel, Murat Sivis, Claus Ropers
Summary: Femtosecond core-level transient absorption spectroscopy was used to investigate the photoinduced dynamics of the charge density wave in 1T-TiSe2. Redshifts in core-level excitations were primarily induced by photoexcited carriers and phonons, with carrier relaxation time and phonon heating time of approximately 360 fs and 1.0 ps, respectively. Oscillations in the absorption spectra were assigned to coherent excitations of the optical A1g phonon and the A?1g charge density wave amplitude mode, and their momentary atomic displacements and amplitudes were determined through simulations.
Article
Nanoscience & Nanotechnology
Finn Zahari, Richard Marquardt, Matthias Kallaene, Ole Gronenberg, Christoph Schlueter, Yury Matveyev, Georg Haberfehlner, Florian Diekmann, Alena Nierhauve, Jens Buck, Arndt Hanff, Gitanjali Kolhatkar, Gerald Kothleitner, Lorenz Kienle, Martin Ziegler, Juergen Carstensen, Kai Rossnagel, Hermann Kohlstedt
Summary: Memristive devices are being developed as non-volatile memory elements to enhance computing capabilities. Interface-based memristive devices are promising for emulating synaptic functionalities in neuromorphic circuits. A device composed of Nb/NbOx/Al2O3/HfO2/Au demonstrates analog switching, no electro-forming, and high current-voltage non-linearity. Spectroscopic evidence and device modeling support the concept of memristive switching based on charge traps within HfO2.
ADVANCED ELECTRONIC MATERIALS
(2023)
Article
Instruments & Instrumentation
Loic Le Guyader, Andrea Eschenlohr, Martin Beye, William Schlotter, Florian Doering, Cammille Carinan, David Hickin, Naman Agarwal, Christine Boeglin, Uwe Bovensiepen, Jens Buck, Robert Carley, Andrea Castoldi, Alessandro D'Elia, Jan-Torben Delitz, Wajid Ehsan, Robin Engel, Florian Erdinger, Hans Fangohr, Peter Fischer, Carlo Fiorini, Alexander Foehlisch, Luca Gelisio, Michael Gensch, Natalia Gerasimova, Rafael Gort, Karsten Hansen, Steffen Hauf, Manuel Izquierdo, Emmanuelle Jal, Ebad Kamil, Suren Karabekyan, Thomas Kluyver, Tim Laarmann, Tobias Lojewski, David Lomidze, Stefano Maffessanti, Talgat Mamyrbayev, Augusto Marcelli, Laurent Mercadier, Giuseppe Mercurio, Piter S. Miedema, Katharina Ollefs, Kai Rossnagel, Benedikt Roesner, Nico Rothenbach, Andrey Samartsev, Justine Schlappa, Kiana Setoodehnia, Gheorghe Sorin Chiuzbaian, Lea Spieker, Christian Stamm, Francesco Stellato, Simone Techert, Martin Teichmann, Monica Turcato, Benjamin Van Kuiken, Heiko Wende, Alexander Yaroslavtsev, Jun Zhu, Serguei Molodtsov, Christian David, Matteo Porro, Andreas Scherz
Summary: Femtosecond transient soft X-ray absorption spectroscopy (XAS) is a promising technique for studying out-of-equilibrium dynamics in material and energy research. This study presents a dedicated setup for soft X-rays at the European XFEL, which uses a beam-splitting zone plate to create three copies of the incoming beam for transmission measurement. Shot-by-shot analysis of transmission is enabled by simultaneously detecting the transmitted intensity through the excited and unexcited sample, as well as monitoring the incoming intensity. An imaging detector with high frame rate and sensitivity is employed for photon detection.
JOURNAL OF SYNCHROTRON RADIATION
(2023)
Article
Chemistry, Physical
Till Domroese, Thomas Danz, Sophie F. Schaible, Kai Rossnagel, Sergey V. Yalunin, Claus Ropers
Summary: The authors discovered a transient hexatic state during the laser-induced transformation between two charge-density wave (CDW) phases in the CDW material 1T-TaS2. The ability to control material properties using light holds great potential for future applications in energy conversion and information technology. Strongly correlated materials such as transition metal dichalcogenides allow for optical control of electronic phases, charge ordering, and interlayer correlations through photodoping.
Article
Microscopy
O. Tkach, T. -P. Vo, O. Fedchenko, K. Medjanik, Y. Lytvynenko, S. Babenkov, D. Vasilyev, Q. L. Nguyen, T. R. F. Peixoto, A. Gloskowskii, C. Schlueter, S. Chernov, M. Hoesch, D. Kutnyakhov, M. Scholz, L. Wenthaus, N. Wind, S. Marotzke, A. Winkelmann, K. Rossnagel, J. Minar, H. -J. Elmers, G. Schonhense
Summary: X-ray photoelectron diffraction (XPD) is a powerful technique that provides detailed structural information of solids and thin films, complementing electronic structure measurements. XPD patterns exhibit pronounced circular dichroism in the angular distribution (CDAD) with asymmetries up to 80%, alongside rapid variations on a small kll-scale. Measurements with circularly-polarized hard X-rays confirm that core-level CDAD is a general phenomenon independent of atomic number.
Article
Materials Science, Multidisciplinary
Yuta Kato, Meng-Jie Huang, Keito Kasebayashi, Takateru Kawakami, Tatsuya Yamaguchi, Jens Buck, Ru-Pan Wang, Matthias Kallaene, Kai Rossnagel, Peter Nagel, Stefan Schuppler, Yoshihiro Takahashi, Takao Odake, Shogo Kawaguchi, Ikuya Yamada, Atsushi Hariki
Summary: We conducted a comprehensive study on A-site ordered perovskite oxides YCu3Co4O12, LaCu3Co4O12, and BiCu3Co4O12, including synthesis, transport, and magnetic characterization, high-pressure application, x-ray absorption spectroscopy, x-ray photoemission spectroscopy, and density-functional theory (DFT) calculations. Our findings reveal insulating behavior and a valence state of A(3+) Cu-3(similar to 3+) Co-4(similar to 3+) O-12(2-) for all three compounds. DFT calculations uncover the energetics of bonding formation and crystal-field splitting, resulting in a narrow-gap electronic structure with hybrid orbitals near the Fermi energy. The presence of hybridization between Co and Cu orbitals is also shown through analysis of experimental spectra.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
H. Beyer, P. Hein, K. Rossnagel, M. Bauer
Summary: Time- and angle-resolved photoelectron spectroscopy was used to investigate the thermalization process of nonequilibrium carrier distribution in the Dirac cone of graphite after absorbing linearly polarized near-infrared laser pulses. The results showed a decay time constant of (20 +/- 3) fs for the photoinduced momentum anisotropy in the initial carrier population. The spectral peak of the initial carriers also exhibited an energy downshift of -100 meV within the first 30 fs, which was attributed to the emission of strongly coupled A'1 optical phonons at K. A fully thermalized distribution was established on a characteristic timescale of (40 +/- 10) fs. These findings highlight the complexity of carrier thermalization on ultrafast timescales, which result from the interplay between carrier-carrier and carrier-phonon interactions.
Article
Materials Science, Multidisciplinary
Masoud Taleb, Fatemeh Davoodi, Florian K. Diekmann, Kai Rossnagel, Nahid Talebi
Summary: This study determines the optical response of WSe2 flakes using cathodoluminescence spectroscopy and reveals strong exciton-photon interaction effects and energy transfer dynamics. Furthermore, confinement effects due to discontinuities in the flakes are demonstrated and used to tailor mode energies, spin-momentum couplings, and exciton-photon coupling strength, as well as to promote photon-mediated exciton-exciton interactions.
ADVANCED PHOTONICS RESEARCH
(2022)
