scholarly journals Attosecond intra-valence band dynamics and resonant-photoemission delays in W(110)

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
S. Heinrich ◽  
T. Saule ◽  
M. Högner ◽  
Y. Cui ◽  
V. S. Yakovlev ◽  
...  
Keyword(s):  
Valence Band ◽  
Photoelectron Spectroscopy ◽  
Electronic Band Structure ◽  
Photoelectric Effect ◽  
Final State ◽  
Electronic Band ◽  
Time Resolved ◽  
Resonant Photoemission ◽  
Pulse Trains ◽  
Electron Correlation Effects

AbstractTime-resolved photoelectron spectroscopy with attosecond precision provides new insights into the photoelectric effect and gives information about the timing of photoemission from different electronic states within the electronic band structure of solids. Electron transport, scattering phenomena and electron-electron correlation effects can be observed on attosecond time scales by timing photoemission from valence band states against that from core states. However, accessing intraband effects was so far particularly challenging due to the simultaneous requirements on energy, momentum and time resolution. Here we report on an experiment utilizing intracavity generated attosecond pulse trains to meet these demands at high flux and high photon energies to measure intraband delays between sp- and d-band states in the valence band photoemission from tungsten and investigate final-state effects in resonant photoemission.

scholarly journals Subpicosecond metamagnetic phase transition driven by non-equilibrium electron dynamics

2021 ◽  
Author(s):  
Federico Pressacco ◽  
Davide Sangalli ◽  
Vojtěch Uhlíř ◽  
Dmytro Kutnyakhov ◽  
Jon Ander Arregi ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Ab Initio ◽  
Photoelectron Spectroscopy ◽  
Electronic Band Structure ◽  
Ferromagnetic Phase ◽  
Electron Dynamics ◽  
Electronic Band ◽  
Time Resolved ◽  
Non Equilibrium

Abstract Femtosecond light-induced phase transitions between different macroscopic orders provide the possibility to tune the functional properties of condensed matter on ultrafast timescales. In first-order phase transitions, transient non-equilibrium phases and inherent phase coexistence often preclude non-ambiguous detection of transition precursors and their temporal onset. Here, we present a study combining time-resolved photoelectron spectroscopy and ab-initio electron dynamics calculations elucidating the transient subpicosecond processes governing the photoinduced generation of ferromagnetic order in antiferromagnetic FeRh. The transient photoemission spectra are accounted for by assuming that not only the occupation of electronic states is modified during the photoexcitation process. Instead, the photo-generated non-thermal distribution of electrons modifies the electronic band structure. The ferromagnetic phase of FeRh, characterized by a minority band near the Fermi energy, is established 350 ± 30 fs after the laser excitation. Ab-initio calculations indicate that the phase transition is initiated by a photoinduced Rh-to-Fe charge transfer.

scholarly journals Subpicosecond metamagnetic phase transition in FeRh driven by non-equilibrium electron dynamics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Federico Pressacco ◽  
Davide Sangalli ◽  
Vojtěch Uhlíř ◽  
Dmytro Kutnyakhov ◽  
Jon Ander Arregi ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Ab Initio ◽  
Photoelectron Spectroscopy ◽  
Electronic Band Structure ◽  
Ferromagnetic Phase ◽  
Electron Dynamics ◽  
Electronic Band ◽  
Time Resolved ◽  
Non Equilibrium

AbstractFemtosecond light-induced phase transitions between different macroscopic orders provide the possibility to tune the functional properties of condensed matter on ultrafast timescales. In first-order phase transitions, transient non-equilibrium phases and inherent phase coexistence often preclude non-ambiguous detection of transition precursors and their temporal onset. Here, we present a study combining time-resolved photoelectron spectroscopy and ab-initio electron dynamics calculations elucidating the transient subpicosecond processes governing the photoinduced generation of ferromagnetic order in antiferromagnetic FeRh. The transient photoemission spectra are accounted for by assuming that not only the occupation of electronic states is modified during the photoexcitation process. Instead, the photo-generated non-thermal distribution of electrons modifies the electronic band structure. The ferromagnetic phase of FeRh, characterized by a minority band near the Fermi energy, is established 350 ± 30 fs after the laser excitation. Ab-initio calculations indicate that the phase transition is initiated by a photoinduced Rh-to-Fe charge transfer.

The effects of (Ba,Sr,Ca)CO3 or LaB6 addition on the x-ray photoelectron spectroscopy spectra and electrical properties of the MgO thin films in alternating current plasma display panels

2008 ◽  
Vol 23 (2) ◽  
pp. 444-451
Author(s):  
Sung Hwan Moon ◽  
Tae Wook Heo ◽  
Sun Young Park ◽  
Jae Hyuk Kim ◽  
Young Chul Choi ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Valence Band ◽  
Photoelectron Spectroscopy ◽  
Electronic Band Structure ◽  
Input Voltage ◽  
Electronic Band ◽  
Plasma Display Panels ◽  
Plasma Display ◽  
Band Spectra

MgO thin films are widely used in plasma display panels (PDPs) to protect the dielectric layer, which is composed of PbO2, B2O3, and SiO2 compound, against ion bombardment during discharge. To improve the electrical properties of the MgO thin films, (Ba,Sr,Ca)CO3 or LaB6, which has a lower work function than that of MgO, added to the MgO films. The effects of (Ba,Sr,Ca)CO3 or LaB6 addition on the electrical properties, microstructure, and electronic band structure were investigated. In the case where (Ba,Sr,Ca)CO3 was added, the firing voltage, which is the voltage when the panel is ignited the first time during increasing input voltage, was about 18.4 V lower than that of the conventional MgO films. In the case where LaB6 was added, the firing voltage was also reduced by about 24 V. The luminance and luminous efficiency were also increased. Of particular interest was the valence band spectra changed after adding (Ba,Sr,Ca)CO3 or LaB6. The valence band edge, which is the top of the valence band, was shifted to lower binding states and the width of the valence band was increased. Moreover, the band gap was slightly reduced. Considering the emission mechanism of MgO films in plasma display panels, these results mean that the secondary electrons can be ejected more easily and the ejected electrons have more energy. Therefore, the addition of (Ba,Sr,Ca)CO3 or LaB6 might improve the electrical properties.

scholarly journals Some Recent Developments in the Photoelectron Spectroscopy of Solids

1999 ◽  
Vol 52 (3) ◽  
pp. 563
Author(s):  
Robert Leckey
Keyword(s):  
Electron Correlation ◽  
Photoelectron Spectroscopy ◽  
Electronic Band Structure ◽  
General Area ◽  
Correlation Effects ◽  
Electronic Band ◽  
Current State ◽  
Structure Determinations ◽  
Recent Developments ◽  
Electron Correlation Effects

A selective review of some recent achievements in the general area of the photoelectron spectroscopy of solids is presented emphasising full hemisphere data collection. The current state of development of both surface structure and electronic band structure determinations is illustrated with an emphasis on materials for which electron correlation effects are significant.

scholarly journals Determination of the valence band edge of Fe oxide nanoparticles dispersed in aqueous solution through resonant photoelectron spectroscopy from a liquid microjet

2021 ◽  
Author(s):  
Giorgia Olivieri ◽  
Gregor Kladnik ◽  
Dean Cvetko ◽  
Matthew A. Brown
Keyword(s):  
Aqueous Solution ◽  
Electronic Structure ◽  
Valence Band ◽  
Photoelectron Spectroscopy ◽  
Band Edge ◽  
Photoemission Spectroscopy ◽  
Oxide Nanoparticles ◽  
Valence Band Edge ◽  
Resonant Photoemission

The electronic structure of hydrated nanoparticles can be unveiled by coupling a liquid microjet with a resonant photoemission spectroscopy.

Theoretical Investigation on Electronic Properties of ZnO Crystals Using DFT-Based Calculation Method

2015 ◽  
Vol 1112 ◽  
pp. 41-44 ◽  
Author(s):  
Yudi Darma ◽  
Freddy Giovanni Setiawan ◽  
Muhammad Aziz Majidi ◽  
Andrivo Rusydi
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Valence Band Maximum ◽  
Band Gaps ◽  
Generalized Gradient ◽  
Strong Electron ◽  
Electronic Band ◽  
Rocksalt Structure

We study the electronic band structure and density of states (DOS) on ZnO material in various crystal structures : wurtzite (W), zincblende (ZB), and rocksalt (RS) phases. Calculations are based on Density Functional Theory (DFT) with Generalized Gradient Approximation (GGA) for exchange-correlation functional and Hubbard correction to consider the strong electron correlations in 3d orbitals. After structural optimization, GGA results show that wurtzite and zincblende structures have a direct band gap of 0.749 eV and 0.637 eV, respectively, whereas rocksalt structure has an indirect band gap of 0.817 eV. Symmetrical shape of total DOS for spin up and spin down electrons indicates a zero total magnetic moment. For all ZnO structures, the upper valence band is formed by hybridization among O 2p and Zn 3d orbitals, while lower valence and conduction band are primarily filled by O 2s and Zn 4s, respectively. The GGA+U approach is found to improve the calculated band gaps and correct the position of Zn 3d state below Valence Band Maximum (VBM). From GGA+U, the band gaps for W-ZnO, ZB-ZnO, and RS-ZnO are 1.12 eV, 1.00 eV, and 1.11 eV, respectively.

scholarly journals Momentum-resolved electronic band structure and offsets in an epitaxial NbN/GaN superconductor/semiconductor heterojunction

2021 ◽  
Author(s):  
Tianlun Yu ◽  
John Wright ◽  
Guru Khalsa ◽  
Betül Pamuk ◽  
Celesta Chang ◽  
...  
Keyword(s):  
Ultrathin Films ◽  
Photoelectron Spectroscopy ◽  
Electronic Band Structure ◽  
Optical Measurements ◽  
First Principles Calculations ◽  
Electronic Band ◽  
Band Bending ◽  
Interfacial States ◽  
Experimental Findings ◽  
Electronic Band Structures

Abstract The electronic structure of heterointerfaces play a pivotal role in their device functionality. Recently, highly crystalline ultrathin films of superconducting NbN have been integrated by molecular beam epitaxy with the semiconducting GaN. We use soft X-ray angle-resolved photoelectron spectroscopy to directly measure the momentum-resolved electronic band structures for both NbN and GaN constituents of this Schottky heterointerface, and determine their momentum-dependent interfacial band offset as well as the band-bending profile into GaN. We find, in particular, that the Fermi states in NbN are aligned against the band gap in GaN, which excludes any significant electronic cross-talk of the superconducting states in NbN through the interface to GaN. We support the experimental findings with first-principles calculations for bulk NbN and GaN. The Schottky barrier height obtained from photoemission is corroborated by electronic transport and optical measurements. The momentum-resolved understanding of electronic properties elucidated by the combined materials advances and experimental methods in our work opens up new possibilities in systems where interfacial states play a defining role.

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