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S Danzenbächer,
Yu Kucherenko,
C Laubschat,
D V Vyalikh,
Z Hossain,
C Geibel, X J Zhou,
W L Yang,
N Mannella,
Z Hussain,
Z-X Shen,
S L Molodtsov
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ABSTRACT: Angle-resolved photoemission spectra of the heavy-fermion system YbIr(2)Si(2) are reported that reveal strong momentum (k) dependent splittings of the 4f(13) bulk and surface emissions around the expected intersection points of the 4f final states with valence bands in the Brillouin zone. The obtained dispersion is explained in terms of a simplified periodic Anderson model by a k dependence of the electron hopping matrix element disregarding clearly interpretation in terms of a single-impurity model.
Physical Review Letters 04/2006; 96(10):106402. · 7.37 Impact Factor
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ABSTRACT: A characteristic feature of the copper oxide high-temperature superconductors is the dichotomy between the electronic excitations along the nodal (diagonal) and antinodal (parallel to the Cu-O bonds) directions in momentum space, generally assumed to be linked to the 'd-wave' symmetry of the superconducting state. Angle-resolved photoemission measurements in the superconducting state have revealed a quasiparticle spectrum with a d-wave gap structure that exhibits a maximum along the antinodal direction and vanishes along the nodal direction. Subsequent measurements have shown that, at low doping levels, this gap structure persists even in the high-temperature metallic state, although the nodal points of the superconducting state spread out in finite 'Fermi arcs'. This is the so-called pseudogap phase, and it has been assumed that it is closely linked to the superconducting state, either by assigning it to fluctuating superconductivity or by invoking orders which are natural competitors of d-wave superconductors. Here we report experimental evidence that a very similar pseudogap state with a nodal-antinodal dichotomous character exists in a system that is markedly different from a superconductor: the ferromagnetic metallic groundstate of the colossal magnetoresistive bilayer manganite La1.2Sr1.8Mn2O7. Our findings therefore cast doubt on the assumption that the pseudogap state in the copper oxides and the nodal-antinodal dichotomy are hallmarks of the superconductivity state.
Nature 12/2005; 438(7067):474-8. · 36.28 Impact Factor
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T Yoshida, X. J. Zhou,
K Tanaka,
W. L. Yang,
Z. Hussain,
Z. -X. Shen,
A. Fujimori,
Seiki Komiya,
Yoichi Ando,
H. Eisaki,
T. Kakeshita,
S Uchida
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ABSTRACT: We have performed a systematic doping dependent study of La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) (0.03$\leq x \leq$0.3) by angle-resolved photoemission spectroscopy. In the entire doping range, the underlying ``Fermi surface" determined from the low energy spectral weight approximately satisfies Luttinger's theorem, even down to the lightly-doped region. This is in strong contrast to the result on Ca$_{2-x}$Na$_x$CuO$_2$Cl$_2$ (Na-CCOC), which shows a strong deviation from Luttinger's theorem. The differences between LSCO and Na-CCOC are correlated with the different behaviors of the chemical potential shift and spectral weight transfer induced by hole doping. Comment: 4 pages, 4 figures
10/2005;
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X J Zhou,
Junren Shi,
T Yoshida,
T Cuk,
W L Yang,
V Brouet,
J Nakamura,
N Mannella,
Seiki Komiya,
Yoichi Ando, [......],
T Sasagawa,
T Kakeshita,
H Eisaki,
S Uchida,
A Fujimori,
Zhenyu Zhang,
E W Plummer,
R B Laughlin,
Z Hussain,
Z-X Shen
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ABSTRACT: High resolution angle-resolved photoemission spectroscopy data along the (0,0)-(pi,pi) nodal direction with significantly improved statistics reveal fine structure in the electron self-energy of the underdoped (La2-xSrx)CuO4 samples in the normal state. Fine structure at energies of (40-46) meV and (58-63) meV, and possible fine structure at energies of (23-29) meV and (75-85) meV, have been identified. These observations indicate that, in (La2-xSrx)CuO4, more than one bosonic modes are involved in the coupling with electrons.
Physical Review Letters 10/2005; 95(11):117001. · 7.37 Impact Factor
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ABSTRACT: From consistency among different measurements, new measurements with better energy resolution, as well as simulations, we show that the fine structure we have identified in the electron self-enery of LSCO is intrinsic, not due to random noise as Valla speculated.
03/2005;
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ABSTRACT: A detailed study of the normal state photoemission lineshapes and quasiparticle dispersion for the single layer Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+\delta}$ (Bi2201) superconductor is presented. We report the first experimental evidence of a double peak structure and a dip of spectral intensity in the energy distribution curves (EDCs) along the nodal direction. The double peak structure is well identified in the normal state, up to ten times the critical temperature. As a result of the same self-energy effect, a strong mass renormalization of the quasiparticle dispersion, i.e. kink, and an increase of the quasiparticle lifetime in the normal state are also observed. Our results provide unambiguous evidence on the existence of bosonic excitation in the normal state, and support a picture where nodal quasiparticles are strongly coupled to the lattice.
01/2005;
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ABSTRACT: We review recent experimental results and phenomenological models of the electron–phonon interaction in high-Tc superconductors as seen by angle-resolved photoemission (ARPES). We focus on the relatively higher doped systems for which the data is reminiscent of a single phonon process and highlight evidence for the relevance of several specific phonon modes to these materials. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (b) 12/2004; 242(1):11 - 29. · 1.32 Impact Factor
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ABSTRACT: We observe, with angle-resolved photoemission, a dramatic change in the electronic structure of two C60 monolayers, deposited, respectively, on Ag (111) and (100) substrates, and similarly doped with potassium to half filling of the C60 lowest unoccupied molecular orbital. The Fermi surface symmetry, the bandwidth, and the curvature of the dispersion at Gamma point are different. Orientations of the C60 molecules on the two substrates are known to be the main structural difference between the two monolayers, and we present new band-structure calculations for some of these orientations. We conclude that orientations play a key role in the electronic structure of fullerides.
Physical Review Letters 12/2004; 93(19):197601. · 7.37 Impact Factor
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ABSTRACT: We report the observation and systematic investigation of the space charge effect and mirror charge effect in photoemission spectroscopy. When pulsed light is incident on a sample, the photo-emitted electrons experience energy redistribution after escaping from the surface because of the Coulomb interaction between them (space charge effect) and between photo-emitted electrons and the distribution of mirror charges in the sample (mirror charge effect). These combined Coulomb interaction effects give rise to an energy shift and a broadening which can be on the order of 10 meV for a typical third-generation synchrotron light source. This value is comparable to many fundamental physical parameters actively studied by photoemission spectroscopy and should be taken seriously in interpreting photoemission data and in designing next generation experiments.
Journal of Electron Spectroscopy and Related Phenomena. 10/2004;
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ABSTRACT: CeTe3 is a layered compound where an incommensurate charge density wave (CDW) opens a large gap ( approximately 400 meV) in optimally nested regions of the Fermi surface (FS), whereas other sections with poorer nesting remain ungapped. Through angle-resolved photoemission, we identify bands backfolded according to the CDW periodicity. They define FS pockets formed by the intersection of the original FS and its CDW replica. Such pockets illustrate very directly the role of nesting in the CDW formation but they could not be detected so far in a CDW system. We address the reasons for the weak intensity of the folded bands, by comparing different foldings coexisting in CeTe3.
Physical Review Letters 10/2004; 93(12):126405. · 7.37 Impact Factor
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T Cuk,
F Baumberger,
D H Lu,
N Ingle, X J Zhou,
H Eisaki,
N Kaneko,
Z Hussain,
T P Devereaux,
N Nagaosa,
Z-X Shen
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ABSTRACT: Angle-resolved photoemission spectroscopy on optimally doped Bi(2)Sr(2)Ca(0.92)Y(0.08)Cu(2)O(8+delta) uncovers a coupling of the electronic bands to a 40 meV mode in an extended k-space region away from the nodal direction, leading to a new interpretation of the strong renormalization of the electronic structure seen in Bi2212. Phenomenological agreements with neutron and Raman experiments suggest that this mode is the B(1g) oxygen bond-buckling phonon. A theoretical calculation based on this assignment reproduces the electronic renormalization seen in the data.
Physical Review Letters 10/2004; 93(11):117003. · 7.37 Impact Factor
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K. Tanaka,
T. Yoshida,
A. Fujimori,
D. H. Lu,
Z.-X. Shen, X.-J. Zhou,
H. Eisaki,
Z. Hussain,
S. Uchida,
Y. Aiura,
K. Ono,
T. Sugaya,
T. Mizuno,
I. Terasaki
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ABSTRACT: Photoemission spectra of underdoped and lightly-doped Bi2−zPbzSr2Ca1−xRxCu2O8+y (R=Pr, Er) (BSCCO) have been measured and compared with those of La2−xSrxCuO4 (LSCO). The lower-Hubbard band of the insulating BSCCO, like Ca2CuO2Cl2, shows a stronger dispersion than La2CuO4 from k∼(π∕2,π∕2) to ∼(π,0). The flat band at k∼(π,0) is found generally deeper in BSCCO. These observations together with the Fermi-surface shapes and the chemical potential shifts indicate that the next-nearest-neighbor hopping ∣t′∣ of the single-band model is larger in BSCCO than in LSCO and that ∣t′∣ rather than the super-exchange J influences the pseudogap energy scale.
Phys. Rev. B. 09/2004; 70(9).
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S.-J. Tang,
Junren Shi,
Biao Wu,
P. T. Sprunger,
W. L. Yang,
V. Brouet, X. J. Zhou,
Z. Hussain,
Z.-X. Shen,
Zhenyu Zhang,
E. W. Plummer
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ABSTRACT: It is now possible to extract from high-resolution angle-resolved photoemission data the Eliashberg function α2F(ω) for electron-phonon coupling (EPC). At the same time, first-principles calculations of the EPC for surface states are appearing in the literature presenting an exquisite picture of the origin of the Eliashberg function. The advances in this field will be illustrated with new data from surface states on two faces of berylium and a direct comparisin to theory for Be(0001). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
physica status solidi (b) 07/2004; 241(10):2345 - 2352. · 1.32 Impact Factor
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Junren Shi,
S-J Tang,
Biao Wu,
P T Sprunger,
W L Yang,
V Brouet, X J Zhou,
Z Hussain,
Z-X Shen,
Zhenyu Zhang,
E W Plummer
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ABSTRACT: We propose a systematic procedure to directly extract the Eliashberg function for electron-phonon coupling from high-resolution angle-resolved photoemission measurement. The procedure is successfully applied to the Be(10(-)10) surface, providing new insights into electron-phonon coupling at this surface. The method is shown to be robust against imperfections in experimental data and suitable for wider applications.
Physical Review Letters 06/2004; 92(18):186401. · 7.37 Impact Factor
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X J Zhou,
T Yoshida,
D-H Lee,
W L Yang,
V Brouet,
F Zhou,
W X Ti,
J W Xiong,
Z X Zhao,
T Sasagawa,
T Kakeshita,
H Eisaki,
S Uchida,
A Fujimori,
Z Hussain,
Z-X Shen
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ABSTRACT: High resolution angle-resolved photoemission measurements on an underdoped (La(2-x)Srx)CuO4 system show that, at energies below 70 meV, the quasiparticle peak is well defined around the (pi/2,pi/2) nodal region and disappears rather abruptly when the momentum is changed from the nodal point to the (pi,0) antinodal point along the underlying "Fermi surface." It indicates that there is an extra low energy scattering mechanism acting upon the antinodal quasiparticles. We propose that this mechanism is the scattering of quasiparticles across the nearly parallel segments of the Fermi surface near the antinodes.
Physical Review Letters 06/2004; 92(18):187001. · 7.37 Impact Factor
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X. J. Zhou,
Junren Shi,
T Yoshida,
T. Cuk,
W. L. Yang,
V. Brouet,
J. Nakamura,
N. Mannella,
Seiki Komiya,
Yoichi Ando, [......],
T Sasagawa,
T. Kakeshita,
H. Eisaki,
S Uchida,
A. Fujimori,
Zhenyu Zhang,
E W Plummer,
R. B. Laughlin,
Z. Hussain,
Z. -X. Shen
[show abstract]
[hide abstract]
ABSTRACT: High resolution angle-resolved photoemission spectroscopy data along the (0,0)-($\pi$,$\pi$) nodal direction with significantly improved statistics reveal fine structure in the electron self-energy of the underdoped (La$_{2-x}$Sr$_x$)CuO$_4$ samples in the normal state. Fine structure at energies of (40$\sim$46) meV and (58$\sim$63)meV, and possible fine structure at energies of (23$\sim$29)meV and (75$\sim$85)meV, have been identified. These observations indicate that, in LSCO, more than one bosonic modes are involved in the coupling with electrons. Comment: 4 pages, 3 figures, Fig. 2 updated
05/2004;
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T. Cuk,
F Baumberger,
D. H. Lu,
N. Ingle, X. J. Zhou,
H. Eisaki,
N. Kaneko,
Z. Hussain,
T. P. Devereaux,
N. Nagaosa,
Z. -X. Shen
[show abstract]
[hide abstract]
ABSTRACT: Angle-resolved photoemission spectroscopy (ARPES) on optimally doped Bi2Sr2Ca0.92Y0.08Cu2O(8+delta) uncovers a coupling of the electronic bands to a 40 meV mode in an extended k-space region away from the nodal direction, leading to a new interpretation of the strong renormalization of the electronic structure seen in Bi2212. Phenomenological agreements with neutron and Raman experiments suggest that this mode is the B1g oxygen bond-buckling phonon. A theoretical calculation based on this assignment reproduces the electronic renormalization seen in the data. Comment: 4 Pages, 4 Figures Updated Figures and Text
03/2004;
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X. J. Zhou,
T Yoshida,
D H Lee,
W. L. Yang,
V. Brouet,
F Zhou,
W. X. Ti,
J. W. Xiong,
Z. X. Zhao,
T Sasagawa,
T. Kakeshita,
H. Eisaki,
S Uchida,
A. Fujimori,
Z. Hussain,
Z. -X. Shen
[show abstract]
[hide abstract]
ABSTRACT: High resolution angle-resolved photoemission measurements on underdoped (La$_{2-x}$Sr$_x$)CuO$_4$ system show that, at energies below 70 meV, the quasiparticle peak is well defined around the ($\pi$/2,$\pi$/2) nodal region and disappears rather abruptly when the momentum is changed from the nodal point to the ($\pi$,0) antinodal point along the underlying ``Fermi surface''. It indicates that there is an extra low energy scattering mechanism acting upon the antinodal quasiparticles. We propose that this mechanism is the scattering of quasiparticles across the nearly parallel segments of the Fermi surface near the antinodes. Comment: to appear in Phys. Rev. Lett
03/2004;
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Physical Review Letters 01/2004; 93:-. · 7.37 Impact Factor
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K Tanaka,
T Yoshida,
A. Fujimori,
D. H. Lu,
Z. -X. Shen, X. J. Zhou,
H. Eisaki,
Z. Hussain,
S Uchida,
Y. Aiura,
K Ono,
T Sugaya,
T Mizuno,
I. Terasaki
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ABSTRACT: Photoemission spectra of underdoped and lightly-doped Bi$_{2-z}$Pb$_z$Sr$_2$Ca$_{1-x}${\it R}$_{x}$Cu$_2$O$_{8+y}$ ($R=$ Pr, Er) (BSCCO) have been measured and compared with those of La$_{2-x}$Sr$_x$CuO$_4$ (LSCO). The lower-Hubbard band of the insulating BSCCO, like Ca$_2$CuO$_2$Cl$_2$, shows a stronger dispersion than La$_2$CuO$_4$ from ${\bf k}\sim$($\pi/2,\pi/2$) to $\sim$($\pi,0$). The flat band at ${\bf k}\sim$($\pi,0$) is found generally deeper in BSCCO. These observations together with the Fermi-surface shapes and the chemical potential shifts indicate that the next-nearest-neighbor hopping $|t^{\prime}|$ of the single-band model is larger in BSCCO than in LSCO and that $|t^{\prime}|$ rather than the super-exchange $J$ influences the pseudogap energy scale. Comment: 5 pages,4 figures, 1 table
12/2003;
