PACS nrs.: 79.60.-i, 71.10.-w, 71.20.Tx, 71.55.Ak.p.-- et al. ; The full three-dimensional dispersion of the π bands, Fermi velocities, and effective masses are measured with angle-resolved photoemission spectroscopy and compared to first-principles calculations. The band structure by density-functional theory underestimates the slope of the bands and the trigonal warping effect. Including electron-electron correlation on the level of the GW approximation, however, yields remarkable improvement in the vicinity of the Fermi level. This demonstrates the breakdown of the independent electron picture in semimetallic graphite and points toward a pronounced role of electron correlation for the interpretation of transport experiments and double-resonant Raman scattering for a wide range of carbon based materials. ; A. G. acknowledges a Marie Curie Individual Fellowship (COMTRANS) from the European Union. T. P. acknowledges DFG Projects No. PI 440/3 and No. 440/4. C.A. and L.W. acknowledge support from the French national research agency. A. R. is supported by the EC Network of Excellence Nanoquanta (No. NMP4-CT-2004-500198), SANES project (No. NMP4-CT-2006-017310), Basque Country University (SGIker Arina), and MEC (No. FIS2007-65702-C02-01). ; Peer reviewed
Two-dimensional organic and metal-organic nanoporous networks can scatter surface electrons, leading to their partial localization. Such quantum states are related to intrinsic surface states of the substrate material. We further corroborate this relation by studying the thermally induced energy shifts of the electronic band stemming from coupled quantum states hosted in a metal-organic array formed by a perylene derivative on Cu(111). We observe by angle-resolved photoemission spectroscopy (ARPES), that both, the Shockley and the partially localized states, shift by the same amount to higher binding energies upon decreasing the sample temperature, providing evidence of their common origin. Our experimental approach and results further support the use of surface states for modelling these systems, which are expected to provide new insight into the physics concerning partially confined electronic states: scattering processes, potential barrier strengths, excited state lifetimes or the influence of guest molecules. ; We acknowledge financial support from the Spanish Ministry of Economy (grant MAT2013-46593-C6-4-P), the Basque Government (grant IT621-13), the Spanish Research Council (CSIC-201560I022), the Swiss Nanoscience Institute (SNI), Swiss National Science Foundation (grants Nos. 200020-149713, 206021-121461), the Netherlands Organization for Scientific Research (NWO Vidi grant No. 700.10.424), the European Research Council (ERC-2012-StG 307760-SURFPRO) and the Paul Scherrer Institute. ; Peer Reviewed
A combined scanning tunneling microscopy, x-ray photoelectron spectroscopy, angle-resolved photoemission spectroscopy, and density functional theory study of graphene on a Fe-Ir(111) alloy with variable Ir concentration is presented. Starting from an intercalated Fe layer between the graphene and Ir(111) surface we find that graphene-substrate interaction can be fine-tuned by Fe-Ir alloying at the interface. When a critical Ir-concentration close to 0.25 is reached in the Fe layer, the Dirac cone of graphene is largely restored and can thereafter be tuned across the Fermi level by further increasing the Ir content. Indeed, our study reveals an abrupt transition between a chemisorbed phase at small Ir concentrations and a physisorbed phase above the critical concentration. The latter phase is highly reminiscent of the graphene on the clean Ir(111) surface. Furthermore, the transition is accompanied by an inversion of the graphene's induced magnetization due to the coupling with the Fe atoms from antiferromagnetic when chemisorbed to weakly ferromagnetic in the physisorption regime, with spin polarizations whose magnitude may be tuned with the amount of Fe content. ; This work has been funded by the Spanish MINECO under contract Nos. FIS2013-48286-C2-1-P, MAT2013-47878-C2-R, MAT2015-66888-C3-1R, and MAT2013-46593-C6-4-P as well as the Basque Government Grants IT621-13 and IT756-13. ; Peer Reviewed
Communication.-- et al. ; A 2D array of electronically coupled quantum boxes is fabricated by means of on-surface self-assembly assuring ultimate precision of each box. The quantum states embedded in the boxes are configured by adsorbates, whose occupancy is controlled with atomic precision. The electronic interbox coupling can be maintained or significantly reduced by proper arrangement of empty and filled boxes. ; The authors would like to acknowledge financial support from the Swiss Nanoscience Institute (SNI), Swiss National Science Foundation (Grants Nos. 200020-149713 and 206021-121461), the Spanish Ministry of Economy (Grant No. MAT2013-46593-C6-4-P), the Basque Government (Grant No. IT621-13), the São Paulo Research Foundation (Grant No. 2013/04855-0), Swiss Government Excellence Scholarship Program, Netherlands Organization for Scientific Research NWO (Chemical Sciences, VIDI-Grant No. 700.10.424), the European Research Council (ERC-2012-StG 307760-SURFPRO), University of Basel, University of Heidelberg, Linköping University, University of Groningen, Paul Scherrer Institute, and the Japan Science and Technology Agency (JST) "Precursory Research for Embryonic Science and Technology (PRESTO)" for a project of "Molecular technology and creation of new function." ; Peer Reviewed
In this paper, we review the development and application of coherent short wavelength light sources implemented using the high harmonic generation (HHG) process. The physics underlying HHG brought quantum physics into the domain of attosecond time-scales for the first time. The observation and manipulation of electron dynamics on such short time-scales—a capability not conceived—of just a few decades ago—is becoming both more-and-more sophisticated and useful as a route to achieve exquisite control over short wavelength light. New experimental techniques are enabling HHG light sources to provide new insights into fundamental quantum interactions in materials, making it possible for the first time to capture the fastest charge, spin, photon and phonon interactions and to achieve diffraction-limited imaging at short wavelengths. ; We gratefully acknowledge support from the National Science Foundation through the JILA Physics Frontiers Center PHY-1734006, and a Gordon and Betty Moore Foundation EPiQS Award GBMF4538, for the attosecond ARPES setups and methods. We gratefully acknowledge support from the Department of Energy Office of Basic Energy Sciences XRay Scattering Program Award DE-SC0002002 for the spin dynamics setups and methods. We gratefully acknowledge support from the Department of EnergyOffice of Basic Energy Sciences AMOS Award DE-FG02-99ER14982 (experiment) as well as an MURI Grant from the Air Force Office of Scientific Research under Award Number FA9550-16-1-0121 (theory) for the HHG light source setups and methods. The authors gratefully acknowledge support from the STROBE National Science Foundation Science and Technology Center, Grant No. DMR-1548924, for the imaging setups and methods. C H-G acknowledges support by Ministerio de Ciencia, Innovación y Universidades for projects (FIS2016-75652-P and PID2019-106910GB-I00) and a Ramon y Cajal contract (RYC-2017-22745), co-funded by the European Social Fund; Junta de Castilla y León and European Union, FEDER, (Project SA287P18); and from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (Grant agreement No. 851201). ZT gratefully acknowledges the financial support from the National Natural Science Foundation of China (Grant No.11874121), the Shanghai Municipal Science and Technology Basic Research Project (Grant No. 19JC1410900) and the Alexander-von-Humboldt foundation.
STM images show that vicinal Au(788) surfaces are made up of a uniform array of (111)-oriented terraces of similar width (∼3.8nm). This uniformity makes it possible to study the electronic structure of the resulting step superlattice by angle-resolved photoemission. We show that for this terrace array the surface state appears to be broken up into one-dimensional quantum-well levels, indicating total electron confinement within the terraces. The angular resolution allows the probability density of the terrace quantum well state to be mapped in reciprocal space, complementing nicely the wave function measured in real space by STM. ; A. Mu., F. J. G. de A., and J. E. O. are supported by the Universidad del País Vasco (1/UPV/EHU/00057.240-EA8078/2000) and the Max Planck Research Award Program. V. R. and S. R. are supported by the CNRS-ULTIMATECH program, the CRIF, and the Université de Paris 7. A. Ma. is supported by a Marie Curie Fellowship of the European Union, under Contract No. HPMF-CT-2000-00565. V. P.-D. is supported by the Comunidad Autónoma de Madrid (Project No. 07N/0042/98) and the DGICYT (Spain) (Grant No. PB-97-1199). ; Peer reviewed
Angular dependence of photoemission time delay for the valence np3/2 and np1/2 subshells of Ar, Kr, and Xe is studied in the dipole relativistic random phase approximation. Strong angular anisotropy of the time delay is reproduced near respective Cooper minima while the spin-orbit splitting affects the time delay near threshold. ; A.S.K. acknowledges the support of the ARC Discovery grant DP120101805. V.K.D. acknowledges the support of the NSF under Grant No. PHY-1305085. P.C.D. acknowledges the support of a grant from the Department of Science and Technology, Government of India. S.T.M. was supported by the Division of Chemical Sciences, Basic Energy Science, Office of Science, US Department of Energy.
Angular dependence of photoemission time delay for the valence np3/2 and np1/2 subshells of Ar, Kr, and Xe is studied in the dipole relativistic random phase approximation. Strong angular anisotropy of the time delay is reproduced near respective Cooper minima while the spin-orbit splitting affects the time delay near threshold. ; A.S.K. acknowledges the support of the ARC Discovery grant DP120101805. V.K.D. acknowledges the support of the NSF under Grant No. PHY-1305085. P.C.D. acknowledges the support of a grant from the Department of Science and Technology, Government of India. S.T.M. was supported by the Division of Chemical Sciences, Basic Energy Science, Office of Science, US Department of Energy.
Financial support provided by Scientific Research Project for Students and Young Researchers Nr. SJZ2015/20 realized at the Institute of Solid State Physics, University of Latvia, is greatly acknowledged. This work has been supported by the Latvian State Research Program on Multifunctional Materials IMIS2. Jennifer Mann from Physical Electronics is greatly acknowledged for providing UPS data. ; Ultraviolet photoelectron spectroscopy (UPS) is commonly used method for energy level determination using planar heterojunction samples in either metal/organic or organic/organic systems. Only some attempts have been made in the study of bulk heterojunction systems. Photoemission yield spectroscopy (PYS) could be applied as a method for organic compound–organic compound interface studies in bulk heterojunction samples. Contrary to the UPS, PYS method does not require ultra-high vacuum, which simplifies experiment setup. Also, scanning depth of PYS is in the range of tens of nanometers, which allows studying deeper layers of the sample instead of only surface layer. In this work, poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) bulk heterojunction thin films were studied as a model system. A mass ratio between P3HT and PCBM in the system was varied from 1:0 to 1:50. Ionization energy dependence on this ratio was studied using two methods: UPS and PYS. To study the influence of the sample morphology on the PYS measurements and obtainable results, phase-separated and homogeneously distributed samples were prepared for analyses. P3HT ionization energy shift of 0.40 eV was observed in the samples made from chloroform solution. Experiments showed the need for a low degree of phase separation between P3HT and PCBM to observe P3HT ionization energy shift using PYS. On the contrary, no ionization energy shift of P3HT was observed in the UPS measurements for the same systems. ; Latvian State Research Program IMIS2; ISSP UL Scientific Research Project for Students and Young Researchers No. SJZ2015/20; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²
En esta tesis presento resultados pormenorizados de investigaciones llevadas a cabo con espectroscopía de emisión óptica resuelta en tiempo de descarga eléctricas tipo rayo en escalas de tiempo poco o nada exploradas (rango del microsegundo y por debajo del microsegundo). Estos estudios han sido realizados con el instrumento GrAnada LIghtning Ultrafast Spectrograph (GALIUS) recientemente desarrollado en nuestro grupo de electricidad atmosférica del Instituto de AstrofÍsica de Andalucía (IAA- CSIC). ; This work has been made possible with the financial assistance of the European Union Horizon 2020 Framework Programme under the Marie Sklodowska-Curie Grant Agreement SAINT 722337 and the Spanish Ministry of Science and Inno vation, under Projects ESP2017-86263-C4-4-R and PID2019-109269RB-C43 and FEDER program ; Financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). ; Peer reviewed
Our first results are about the analysis of optical emission spectra from lightninglike electrical discharges recorded at 2.1 Mfps with grism R3. These are the first time-resolved spectra obtained with high-speed framing cameras at sub- microsecond timescales. Quantifications from these spectra revealed evidences of non-LTE conditions right behind the shock front in posttrigger sub-microsecond times. We published these results in a paper in Geophysical Research Letters with title \Sub-microsecond Spectroscopy of Lightning-Like Discharges: Exploring New Time Regimes" (Kieu et al., 2020). At lower recording speeds, GALIUS was capable of filming lightning-like discharges from the near ultraviolet-blue to the near-infrared with grisms R1, R2, R4. We found evidences of molecular optical emissions from CO, CN, C2, N2, and N + 2 . This nding may open the door to identify and quantify lightning NO production by using high-speed optical emission spectroscopy. From the emissions of different spectral lines, electron concentrations and gas temperatures were estimated by different methods and compared with each other. These results were published in a paper in Journal of Geophysical Research Atmospheres with title \High-speed spectroscopy lightning-like discharges: evidence of molecular optical emissions" (Kieu et al., 2021). ; Los primeros resultados de la tesis provienen del analisis de los espectros ópticos resueltos en tiempo de descargas eléctricas tipo rayo obtenido a 2.1 Mfps con el \grisma" R3. Hasta la fecha son los primeros y únicos espectros de descargas el ectricas tipo rayo obtenidos con un espectrógrafo de imagen con resolución temporal inferior al microsegundo (y con tiempos de exposición de 160 nanosegundos). Los análisis de los espectros sugieren un posible alejamiento de las condiciones de equilibrio termodinámico local (LTE) justo detrás del frente de propagación de la onda de choque asociada a la expansión del canal de la descarga en los instantes inmediatamente posteriores al comienzo de la misma y en una escala de tiempo inferior al microsegundo. Estos resultados se incluyen en un artículo de título \Sub-microsecond Spectroscopy of Lightning-Like Discharges: Exploring New Time Regimes" publicado en la revista de alto impacto Geophysical Research Letters (Kieu et al., 2020). Al usar GALIUS con velocidades de grabación inferior a los 2.1 Mfps hemos podido disponer también de espectros ópticos desde el rango ultravioleta cercano hasta el infrarrojo cercano usando los \grismas" R1, R2 y R4. En este estudio se han encontrado evidencias de emisiones ópticas moleculares asociadas a las especies CO, CN, C2, N2 y N + 2 , algunas de las cuales (CO y C2) se han detectado por primera vez en el canal de descargas eléctricas tipo rayo. Estos hallazgos hacen pensar en la posibilidad futura de detectar, en el rango espectral entre 140 nm y 340 nm, emisiones ópticas asociadas al _oxido de nitrógeno (NO) producido por los rayos y descargas tipo rayo (GALIUS solo es sensible hasta los 380 nm). A partir del análisis de diferentes líneas espectrales se han cuantificado por diferentes métodos (que se han comparado entre s__) temperaturas y concentración de electrones en el canal de las descargas tipo rayo investigadas. Estos resultados se incluyen en un artículo de título \High-speed spectroscopy of lightning-like dis- charges: evidence of molecular optical emissions" publicado en la revista de alto impacto Journal of Geophysical Research - Atmospheres (Kieu et al., 2021). ; Tesis Univ. Granada. ; European Union Horizon 2020 Framework Programme under the Marie Sklodowska-Curie Grant Agreement SAINT 722337 ; Spanish Ministry of Science and Innovation, under Projects ESP2017-86263-C4-4-R and PID2019-109269RB-C43 and FEDER program
