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ABSTRACT: The low-energy electronic structure of the [Formula: see text] spin-orbit insulator Sr(3)Ir(2)O(7) has been studied by means of angle-resolved photoemission spectroscopy. A comparison of the results for bilayer Sr(3)Ir(2)O(7) with available literature data for the related single-layer compound Sr(2)IrO(4) reveals qualitative similarities and similar [Formula: see text] bandwidths for the two materials, but also pronounced differences in the distribution of the spectral weight. In particular, photoemission from the [Formula: see text] states appears to be suppressed. Yet, it is found that the Sr(3)Ir(2)O(7) data are in overall better agreement with band-structure calculations than the data for Sr(2)IrO(4).
Journal of Physics Condensed Matter 09/2012; 24(41):415602. · 2.55 Impact Factor
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ABSTRACT: The low-energy electronic structure of the J_{eff}=1/2 spin-orbit insulator
Sr3Ir2O7 has been studied by means of angle-resolved photoemission
spectroscopy. A comparison of the results for bilayer Sr3Ir2O7 with available
literature data for the related single-layer compound Sr2IrO4 reveals
qualitative similarities and similar J_{eff}=1/2 bandwidths for the two
materials, but also pronounced differences in the distribution of the spectral
weight. In particuar, photoemission from the J_{eff}=1/2 states appears to be
suppressed. Yet, it is found that the Sr3Ir2O7 data are in overall better
agreement with band-structure calculations than the data for Sr2IrO4.
07/2012;
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ABSTRACT: Topological insulators with mass-less helical Dirac fermions on their surface
have attracted considerable attention in recent years. Several exotic effects
and proposed applications rely on the presence of such states also at the
interface between a topological insulator and a trivial insulator. In the
present work, we have used low-energy angle-resolved photoelectron spectroscopy
to demonstrate and characterize the interface states at the substrate interface
in Bi2Se3 thin films grown on Si(111). The results establish that Dirac
fermions are indeed present also at the interface. It is also shown that the
interface states are shifted in energy with respect to the surface states due
to band bending in the film. The observation of topological interface states
paves the way for further studies of interface related phenomena involving
topological insulator thin films.
06/2012;
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ABSTRACT: We present an experimental setup for laser-based angle-resolved time-of-flight photoemission. Using a picosecond pulsed laser, photons of energy 10.5 eV are generated through higher harmonic generation in xenon. The high repetition rate of the light source, variable between 0.2 and 8 MHz, enables high photoelectron count rates and short acquisition times. By using a time-of-flight analyzer with angle-resolving capabilities, electrons emitted from the sample within a circular cone of up to ±15° can be collected. Hence, simultaneous acquisition of photoemission data for a complete area of the Brillouin zone is possible. The current photon energy enables bulk sensitive measurements, high angular resolution, and the resulting covered momentum space is large enough to enclose the entire Brillouin zone in cuprate high-T(c) superconductors. Fermi edge measurements on polycrystalline Au shows an energy resolution better than 5 meV. Data from a test measurement of the Au(111) surface state are presented along with measurements of the Fermi surface of the high-T(c) superconductor Bi(2)Sr(2)CaCu(2)O(8 + δ) (Bi2212).
The Review of scientific instruments 09/2011; 82(9):095113. · 1.52 Impact Factor
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E Razzoli,
Y Sassa,
G Drachuck,
M Månsson,
A Keren,
M Shay,
M H Berntsen, O Tjernberg,
M Radovic,
J Chang,
S Pailhès,
N Momono,
M Oda,
M Ido,
O J Lipscombe,
S M Hayden,
L Patthey,
J Mesot,
M Shi
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ABSTRACT: A systematic angle-resolved photoemission study of the electronic structure of La2−xSrxCuO4 in a wide doping range is presented in this paper. In addition to the main energy band, we observed a weaker additional band, the (π, π) folded band, which shows unusual doping dependence. The appearance of the folded band suggests that a Fermi surface reconstruction is doping dependent and could already occur at zero magnetic field.
New Journal of Physics 12/2010; 12(12):125003. · 4.18 Impact Factor
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ABSTRACT: A new type of hemispherical electron energy analyzer that permits angle and spin resolved photoelectron spectroscopy has been developed. The analyzer permits standard angle resolved spectra to be recorded with a two-dimensional detector in parallel with spin detection using a mini-Mott polarimeter. General design considerations as well as technical solutions are discussed and test results from the Au(111) surface state are presented.
The Review of scientific instruments 03/2010; 81(3):035104. · 1.52 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: A new type of hemispherical electron energy analyzer that permits angle and spin resolved photoelectron spectroscopy has been developed. The analyzer permits standard angle resolved spectra to be recorded with a two-dimensional detector in parallel with spin detection using a mini-Mott polarimeter. General design considerations as well as technical solutions are discussed and test results from the Au(111) surface state are presented.
01/2010;
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E. Papalazarou,
Matteo Gatti,
M. Marsi,
V. Brouet,
F. Iori,
Lucia Reining,
E. Annese,
I. Vobornik,
F. Offi,
A. Fondacaro,
S. Huotari,
P. Lacovig, O. Tjernberg,
N. B. Brookes,
M. Sacchi,
P. Metcalf,
G. Panaccione
[show abstract]
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ABSTRACT: We present a comprehensive study of the photon energy dependence of the valence band photoemission yield in the prototype Mott-Hubbard oxide V2O3. The analysis of our experimental results, covering an extended photon energy range (20-6000 eV) and combined with GW calculations, allow us to identify the nature of the orbitals contributing to the total spectral weight at different binding energies, and in particular to locate the V 4s at about 8 eV binding energy. From this comparative analysis we can conclude that the intensity of the quasiparticle photoemission peak, observed close to the Fermi level in the paramagnetic metallic phase upon increasing photon energy, does not have a significant correlation with the intensity variation of the O 2p and V 3d yield, thus confirming that bulk sensitivity is an essential requirement for the detection of this coherent low energy excitation.
04/2009;
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ABSTRACT: The charge density in solids is a fundamental parameter. Here we demonstrate that the charge density can be determined by the use of angle resolved photoelectron spectroscopy. The method, which involves a Fourier-like transform from momentum space to real space, is demonstrated by utilizing soft x-ray angle resolved photoelectron spectroscopy to sample the complete three-dimensional Brillouin zone of copper. It is also shown that this can be done in an energy resolved way as to extract the charge density contribution from states of a particular energy.
Physical Review Letters 12/2008; 101(22):226404. · 7.37 Impact Factor
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J. Chang,
M. Shi,
S. Pailhés,
M. Månsson,
T. Claesson, O. Tjernberg,
A. Bendounan,
Y. Sassa,
L. Patthey,
N. Momono,
M. Oda,
M. Ido,
S. Guerrero,
C. Mudry,
J. Mesot
[show abstract]
[hide abstract]
ABSTRACT: An angle-resolved photoemission study of the scattering rate in the superconducting phase of the high-temperature superconductor La2−xSrxCuO4 with x=0.145 and x=0.17, as a function of binding energy and momentum, is presented. We observe that the scattering rate scales linearly with binding energy up to the high-energy scale E1∼0.4 eV. The scattering rate is found to be strongly anisotropic, with a minimum along the (0,0)–(π,π) direction. A possible connection to a quantum-critical point is discussed.
Phys. Rev. B. 11/2008; 78(20).
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M Shi,
A. Bendounan,
E. Razzoli,
S. Rosenkranz,
M. R. Norman,
J. C. Campuzano,
J Chang,
M. Mansson,
Y. Sassa,
T. Claesson, O. Tjernberg,
L. Patthey,
N. Momono,
M Oda,
M. Ido,
S. Guerrero,
C. Mudry,
J. Mesot
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ABSTRACT: Angle-resolved photoemission on underdoped La$_{1.895}$Sr$_{0.105}$CuO$_4$ reveals that in the pseudogap phase, the dispersion has two branches located above and below the Fermi level with a minimum at the Fermi momentum. This is characteristic of the Bogoliubov dispersion in the superconducting state. We also observe that the superconducting and pseudogaps have the same d-wave form with the same amplitude. Our observations provide direct evidence for preformed Cooper pairs, implying that the pseudogap phase is a precursor to superconductivity.
10/2008;
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M Shi,
J Chang,
S Pailhés,
M R Norman,
J C Campuzano,
M Månsson,
T Claesson, O Tjernberg,
A Bendounan,
L Patthey,
N Momono,
M Oda,
M Ido,
C Mudry,
J Mesot
[show abstract]
[hide abstract]
ABSTRACT: We present angle-resolved photoemission spectroscopy data on moderately underdoped La1.855Sr0.145CuO4 at temperatures below and above the superconducting transition temperature. Unlike previous studies of this material, we observe sharp spectral peaks along the entire underlying Fermi surface in the superconducting state. These peaks trace out an energy gap that follows a simple d-wave form, with a maximum superconducting gap of 14 meV. Our results are consistent with a single gap picture for the cuprates. Furthermore our data on the even more underdoped sample La1.895Sr0.105CuO4 also show sharp spectral peaks, even at the antinode, with a maximum superconducting gap of 26 meV.
Physical Review Letters 08/2008; 101(4):047002. · 7.37 Impact Factor
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J Chang,
Y. Sassa,
S. Guerrero,
M. Mansson,
M Shi,
S. Pailhes,
A. Bendounan,
R. Mottl,
T. Claesson, O. Tjernberg,
L. Patthey,
M. Ido,
N. Momono,
M Oda,
C. Mudry,
J. Mesot
[show abstract]
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ABSTRACT: We report an angle resolved photoemission study of the electronic structure of the pseudogap state in \NdLSCO ($T_c<7$ K). Two opposite dispersing Fermi arcs are the main result of this study. The several scenarios that can explain this observation are discussed. Comment: A high-resolution version can be found at http://lns.web.psi.ch/lns/download/Pockets/arXiv.pdf
05/2008;
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J Chang,
Y Sassa,
S Guerrero,
M Månsson,
M Shi,
S Pailhés,
A Bendounan,
R Mottl,
T Claesson, O Tjernberg,
L Patthey,
M Ido,
N Momono,
M Oda,
C Mudry,
J Mesot
[show abstract]
[hide abstract]
ABSTRACT: We report an angle resolved photoemission study of the electronic structure of the pseudogap state in La1.48Nd0.4Sr0.12CuO4 (Tc < 7 K). Two opposite dispersing Fermi arcs consistent with the existence of a small hole-like Fermi pocket is the main result of this study.
04/2008;
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G. Panaccione,
F. Offi,
P. Torelli,
G. Vanko, O. Tjernberg,
P. Lacovig,
A. Guarino,
A. Fondacaro,
A. Nigro,
M. Sacchi,
N. B. Brookes,
G. Monaco
[show abstract]
[hide abstract]
ABSTRACT: We report core level and valence band photoemission results obtained for Nd2−xCexCuO4 (x=0.15) single crystals and films by using both soft and hard x rays, hence, with tunable depth sensitivity. When using hard x rays only, we observe distinct and energy separated structures in the main 2p53d9L peak of Cu 2p3/2 and 2p1/2 core levels, including the well screened features located at the high kinetic energy side, which were recently reported by Taguchi et al. Phys. Rev. Lett. 95 177002 (2005)]. By varying the photoelectron takeoff angle, we analyze the difference in the screening properties between surface and bulk, and we demonstrate the depth dependence of the electronic properties by following the evolution of the bulk-related peak. The possible influence of the surface conditions on the Cu 2p spectral features is also discussed.
Phys. Rev. B. 03/2008; 77(12).
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T. Claesson,
M. Mansson,
A. Önsten,
M Shi,
S Pailhés,
J Chang,
Y. Sassa,
A. Bendounan,
L. Patthey,
J. Mesot,
T Muro,
T Matsushita,
T Kinoshita,
T Nakamura,
N. Momono,
M Oda,
M. Ido, O. Tjernberg
[show abstract]
[hide abstract]
ABSTRACT: We present angle-resolved photoelectron spectroscopy data probing the electronic structure of the Nd-substituted high-$T_c$ cuprate La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$ (Nd-LSCO). Data have been acquired at low and high photon energies, $h\nu$ = 55 and 500 eV, respectively. Earlier comparable low-energy studies of La$_{1.4-x}$Nd$_{0.6}$Sr$_{x}$CuO$_4$ ($x = 0.10, 0.12, 0.15$) have shown strongly suppressed photoemission intensity, or absence thereof, in large parts of the Brillouin zone. Contrary to these findings we observe spectral weight at all points along the entire Fermi surface contour at low and high photon energies. No signs of strong charge modulations are found. At high photon energy, the Fermi surface shows obvious differences in shape as compared to the low-energy results presented here and in similar studies. The observed difference in shape and the high bulk-sensitivity at this photon energy suggest intrinsic electronic structure differences between the surface and bulk regions.
01/2008;
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J Chang,
M Shi,
S. Pailhes,
M. Maansson,
T. Claesson, O. Tjernberg,
A. Bendounan,
Y. Sassa,
L. Patthey,
N. Momono,
M Oda,
M. Ido,
S. Guerrero C. Mudry,
J. Mesot
[show abstract]
[hide abstract]
ABSTRACT: An angle-resolved photoemission study of the scattering rate in the superconducting phase of the high-temperature superconductor \LSCO\ with $x=0.145$ and $x=0.17$, as a function of binding energy and momentum, is presented. We observe that the scattering rate scales linearly with binding energy up to the high-energy scale $E_1\sim0.4$ eV. The scattering rate is found to be strongly anisotropic, with a minimum along the (0,0)-($\pi,\pi$) direction. A possible connection to a quantum-critical point is discussed. Comment: Final version published in PRB
08/2007;
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M Shi,
J Chang,
S Pailhés,
M. R. Norman,
J. C. Campuzano,
M. Mansson,
T. Claesson, O. Tjernberg,
A. Bendounan,
L. Patthey,
N. Momono,
M Oda,
M. Ido,
C. Mudry,
J. Mesot
[show abstract]
[hide abstract]
ABSTRACT: We present angle-resolved photoemission spectroscopy (ARPES) data on moderately underdoped La$_{1.855}$Sr$_{0.145}$CuO$_4$ at temperatures below and above the superconducting transition temperature. Unlike previous studies of this material, we observe sharp spectral peaks along the entire underlying Fermi surface in the superconducting state. These peaks trace out an energy gap that follows a simple {\it d}-wave form, with a maximum superconducting gap of 14 meV. Our results are consistent with a single gap picture for the cuprates. Furthermore our data on the even more underdoped sample La$_{1.895}$Sr$_{0.105}$CuO$_4$ also show sharp spectral peaks, even at the antinode, with a maximum superconducting gap of 26 meV. Comment: Accepted by Phys. Rev. Lett
08/2007;
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J. Chang,
S. Pailhés,
M. Shi,
M. Månsson,
T. Claesson, O. Tjernberg,
J. Voigt,
V. Perez,
L. Patthey,
N. Momono,
M. Oda,
M. Ido,
A. Schnyder,
C. Mudry,
J. Mesot
[show abstract]
[hide abstract]
ABSTRACT: The existence of coherent quasiparticles near the Fermi energy in the low-temperature state of high-temperature superconductors has been well established by angle-resolved photoemission spectroscopy (ARPES). We present a study of La1.83Sr0.17CuO4 in the superconducting state and report an abrupt change in the quasiparticle spectral function, as we follow the dispersion of the ARPES signal from the Fermi energy to 0.6 eV. The interruption in the quasiparticle dispersion separates coherent quasiparticle peaks at low energies from broad incoherent excitations at high energies. We find that the boundary between these low-energy and high-energy features exhibits a cosine-shaped momentum dependence, reminiscent of the superconducting d-wave gap. Further intriguing similarities between characteristics of the incoherent excitations and quasiparticle properties suggest a close relation between the electronic response at high and low energies in cuprate superconductors.
Phys. Rev. B. 06/2007; 75(22).
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G Panaccione,
M Altarelli,
A Fondacaro,
A Georges,
S Huotari,
P Lacovig,
A Lichtenstein,
P Metcalf,
G Monaco,
F Offi,
L Paolasini,
A Poteryaev, O Tjernberg,
M Sacchi
[show abstract]
[hide abstract]
ABSTRACT: We have measured hard x-ray photoemission spectra of pure vanadium sesquioxide (V(2)O(3)) across its metal-insulator transition. We show that, in the metallic phase, a clear correlation exists between the shakedown satellites observed in the vanadium 2p and 3p core-level spectra and the coherent peak measured at the Fermi level. Comparing experimental results and dynamical mean-field theory calculations, we estimate the Hubbard energy U in V(2)O(3) (4.20+/-0.05 eV). From our bulk-sensitive photoemission spectra we infer the existence of a critical probing depth for investigating electronic properties in strongly correlated solids.
Physical Review Letters 10/2006; 97(11):116401. · 7.37 Impact Factor
