Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session N9: Superconductivity: Oxide Photoemission II |
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Sponsoring Units: DMP Chair: Michael Fluss, Lawrence Livermore National Laboratory Room: Colorado Convention Center Korbel 1D |
Wednesday, March 7, 2007 8:00AM - 8:12AM |
N9.00001: Theory of Photoemission Line Shape in High Temperature Superconducter $Bi_2Sr_2CaCu_2O_{8+\delta}$ via Dipolon Mediated Electron-Electron Pairing Mechanism Ram Sharma Observed photoemission (PE) line shape near ($\pi$,0) in superconductor BISCCO containing a peak, a dip and a broad feature has been explained naturally by dipolon pairing mechanism using temperature dependent expressions [1,2] including all necessary and important electron correlations. The calculated positions of the peak, dip and broad feature agree well with the observed results.The theory predicts the possibility of observing dipolon side bands in PE. Contributions not only from nearest $Cu-O_2$ layer but also from all other layers and rows are important. The peak in PE is due to excitation solely of a quasiparticle; the broad feature and dip are due to the excitations of quasiparticles with concomitant O(1,1) and O(1,2) dipolon excitations. In normal state PE [3] of UD, Op and OD samples we have identified these dipolon excitations. Matrix element effects have been considered. \newline \newline [1] R.R. Sharma, Phy. Rev. {\bf B 63}, 054506 (2001). \newline [2] R. R. Sharma, Physica {\bf C 439}, 47 (2006). \newline [3] Y.-D. Chuang, Phy. Rev. {\bf B 69}, 094515 (2004). [Preview Abstract] |
Wednesday, March 7, 2007 8:12AM - 8:24AM |
N9.00002: Van Hove singularity crossing in overdoped superconducting cuprates - effect on superconducting and normal-state properties Jeffery L. Tallon, James Storey, Tobias Fellmeth, Grant Williams We show from modelling the entropy, superfluid density and thermoelectric power using a rigid ARPES-derived dispersion that the crossing of the van Hove singularity (vHs) occurs in Bi$_2$Sr$_2$CaCu$_2$O$_8$ in the heavily overdoped region at a hole concentration of p=0.22 holes per Cu. This concurs with recent results from ARPES measurements. The impact of the vHs crossing on the thermodynamic properties, the Knight shift and susceptibility, transport, optical and superconducting properties is described and shown to account for much of the overall doping dependence of these properties. The only exotic feature that needs to be introduced is the pseudogap showing that much of the physics of HTS materials is conventional. These insights help us to see that the ``lost entropy'' of 1kB per doped hole, previously associated with the pseudogap, is just associated with the DOS asymmetry arising from the proximity of the vHs. Remarkable is the insensitivity of the doping dependence of Tc to the singularity in the DOS. [Preview Abstract] |
Wednesday, March 7, 2007 8:24AM - 8:36AM |
N9.00003: Distinct Fermi-momentum dependent energy gaps in deeply underdoped Bi2212. K. Tanaka, W.S. Lee, D.H. Lu, A. Fujimori, T. Fujii, * Risdiana, I. Terasaki, K. Fujita, M. Ishikado, S. Uchida, D.J. Scalapino, T.P. Devereaux, Z. Hussain, Z.-X. Shen Our recent angle-resolved photoemission spectroscopy study of deeply underdoped cuprate superconductors Bi2Sr2(Ca,R)Cu2O8 (R = Y or Dy) (Bi2212) suggested the presence of two distinct energy gaps exhibiting different doping dependences [1]. One gap, associated with the antinodal region where no coherent peak is observed, increases with underdoping - a behavior known for more than a decade and considered as the general behavior of the gap in the underdoped regime. The other gap, associated with the near nodal regime where a coherent peak can be observed in energy distribution curves (EDCs), does not increase with less doping - a behavior not seen in the single particle spectra before. The theoretical implications of these findings and temperature dependence of the spectra will be discussed. [1] Science, in press. (http://www.sciencemag.org/cgi/content/abstract/1133411) [Preview Abstract] |
Wednesday, March 7, 2007 8:36AM - 8:48AM |
N9.00004: Detail Properties of Band Renormalization Effect of the Bi$_{2}$Sr$_{2}$Ca$_{1}$Cu$_{2}$O$_{8+\delta }$ Wei-Sheng Lee, Worawat Meevesana, Donghui Lu, Steve Johnston, Tomas Devereaux, Hiroshi Eisaki, Zhi-Xun Shen Since the observation of a kink in the nodal dispersion and the peak-dip-hump structure at antinodal region, the band renormalization effects in High-Tc superconducting cuprates have drawn lots of attention in the field of High-Tc superconductivity. Despite of the consensus that these renormalization structures are induced by coupling to some bosonic mode(s), data with much improved quality are needed to clarify the origin of the mode and gain further insight into its relation to the High-Tc superconductivity. In this work, detailed temperature and doping dependence of the band renormalization effect in Bi2212 system are studied via ARPES spectra with improved data quality. Our data suggest that there are multiple bosonic modes coupled to the electrons exhibiting a rich superconductivity and doping induced phenomena. Simulations based on electron-phonon interaction will also be discussed in comparison to our data. [Preview Abstract] |
Wednesday, March 7, 2007 8:48AM - 9:00AM |
N9.00005: Evidence for two energy scales in the superconducting state of optimally doped (Bi,Pb)$_2$(Sr,La)$_2$CuO$_{6+\delta}$ Takeshi Kondo, Tsunehiro Takeuchi, Syunsuke Tsuda, Shik Shin, Adam Kaminski We use angle-resolved photoemission spectroscopy (ARPES) to investigate the properties of energy gap(s) in the optimally doped (Bi,Pb)$_2$(Sr,La)$_2$CuO$_{6+ \delta}$ (Bi2201). We find significant differences in the momentum- and temperature- dependence of the pseudogap and supercondcuting gap suggesting that these gaps have two separate energy scales. The ARPES spectra slightly off the node have a sharp peak with a small gap below $T_c$, which closes at $T_c$. Around the antinode, the broad spectra with a large energy gap of $\sim$40meV are observed above and below $T_c$. The spectral shape and the gap size around the antinod are almost unchanged across $T_c$, indicating that the pseudogap state coexists with superconducting state below $T_c$, and it dominates the character of ARPES spectra around antinode. We speculate that the pseudogap state competes with superconductivity by diminishing spectral weight in the superconducting antinode. [Preview Abstract] |
Wednesday, March 7, 2007 9:00AM - 9:12AM |
N9.00006: Laser-ARPES studies of BSCCO-BASED cuprate superconductors J.F. Douglas, J.D. Koralek, Z. Sun, N.C. Plumb, Q. Wang, T.J. Reber, J.D. Griffith, Y. Aiura, K. Oka, H. Eisaki, D.S. Dessau, T.P. Devereaux, S.S. Johnson Utilizing 6 eV and 7 eV laser light, we have performed high-resolution ANGLE RESOLVED PHOTOEMISSION studies of the BSCCO family of superconductors. This higher resolution, in both energy and momentum, has allowed the observation of interesting new doping- and temperature-dependent features in the nodal and near nodal dispersions in these materials. [Preview Abstract] |
Wednesday, March 7, 2007 9:12AM - 9:24AM |
N9.00007: VUV Laser-Based ARPES on Electronic Structure of High Temperature Superconductors Xingjiang Zhou, Guodong Liu, Wentao Zhang, Haiyun Liu, Lin Zhao, Jianqiao Meng, Xiaoli Dong, Z.Y. Xu, G.L. Wang, H.B. Zhang, Y. Zhou, C.T. Chen, Y. Zhu, G.C. Zhang, X.H. Wen, G.D. Gu The last decade has witnessed a dramatic improvement of the angle-resolved photoemission spectroscopy (ARPES) technique in terms of energy and momentum resolution. This in turn has resulted in a number of new findings on the electronic structure of high-Tc cuprate superconductors, particularly the identification of many-body effects. In this talk, we will present results on the electronic structure of high-Tc superconductors measured from our new ARPES system based on VUV laser, realized by frequency doubling from a non-linear optical crystal KBBF. The laser-based ARPES system has ultra-high energy resolution, high photon flux, and a potential to enhance bulk sensitivity. [Preview Abstract] |
Wednesday, March 7, 2007 9:24AM - 9:36AM |
N9.00008: Protected nodes and the collapse of the Fermi arcs in high $T_{c}$ cuprates Amit Kanigel, U. Chatterjee, M. Randeria, M.R. Norman, S. Souma, M. Shi, Z.Z. Li, H. Raffy, J.C. Campuzano Angle resolved photoemission studies on underdoped samples of Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$ reveal that the superconducting gap's magnitude and anisotropy remain unchanged up to $T_{c}$. Above $T_{c}$, the nodes of the d-wave gap abruptly expand into finite length Fermi arcs. As this change occurs within the resistive width of the transition, we argue that the Fermi arcs are not simply thermally broadened nodes, but rather a unique signature of the pseudogap phase. This is in contrast to BCS theory, which predicts a gap with fixed anisotropy that changes with temperature and disappears above $T_{c}$. [Preview Abstract] |
Wednesday, March 7, 2007 9:36AM - 9:48AM |
N9.00009: The Shrinking ``Fermi Arc'' in Cuprates Lijun Zhu, C. M. Varma The angle-resolved photoemission spectroscopy (ARPES) on cuprates in the pseudogap region reveal an extraordinary topological transition in which the ground state changes from one with a usual Fermi surface to one with four Fermi points. We argue that such a state is not possible without some symmetry breaking which allows interference between one-particle basis states which is normally forbidden. We also show that the experimental results are quantitatively given without any free parameters by a theory and discuss the implications of the results. [Preview Abstract] |
Wednesday, March 7, 2007 9:48AM - 10:00AM |
N9.00010: ABSTRACT WITHDRAWN |
Wednesday, March 7, 2007 10:00AM - 10:12AM |
N9.00011: Nature of the quasiparticle remnant in La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) A. Bansil, S. Sahrakorpi, R.S. Markiewicz, M. Lindroos, V. Arpiainen, X.J. Zhou, T. Yoshida, W.L. Yang, T. Kakeshita, H. Eisaki, S. Uchida, A. Fujimori, Z. Hussain, Z.-X. Shen Angle resolved photoemission (ARPES) studies in LSCO have revealed a remarkable state of affairs in that the observed Fermi surface maps are in excellent accord with the LDA calculations even in the highly underdoped regime. Here we demonstrate that the agreement with gross band dispersion persists to quite high energy scales of several hundred meV's. For example, even in the 3\%-doped sample, the position and shape of the van Hove singularity is found to be in accord with LDA predictions. Signatures of strong correlation physics are manifest however through the suppression of spectral weight near the Fermi energy particularly in the underdoped system. In this way, even though the gross dispersion is virtually unrenormalized, there is a strong renormalization of the spectral weight. Work supported in part by the USDOE. [Preview Abstract] |
Wednesday, March 7, 2007 10:12AM - 10:24AM |
N9.00012: Universal spectral weight transfer in high temperature superconductors Jeff Graf, Gey-Hong Gweon, Kyle McElroy, Shuyun Zhou, Chris Jozwiak, Eli Rotenberg, Andreas Bill, T. Sasagawa, H. Eisaki, S. Uchida, H. Takagi, Dung-Hai Lee, Alessandra Lanzara High resolution angle resolved photoemission spectroscopy (ARPES) studies of the electronic structure of several cuprate families, over the entire phase diagram, from undoped to highly overdoped regime are reported. A detailed study of the one-electron dynamics as a function of momentum, temperature and doping is presented. A universal spectral weight transfer is observed for all systems and discussed in terms of a strong interplay between the electron-lattice and electron-electron interaction in these materials. [Preview Abstract] |
Wednesday, March 7, 2007 10:24AM - 10:36AM |
N9.00013: Spectral properties of the Hubbard-Holstein model and comparison to ARPES experiments in the copper oxides Brian Moritz, Alexandru Macridin, Ehsan Khatami, Francois Vernay, Thomas Maier, Thomas P. Devereaux, Mark Jarrell We employ a dynamical cluster Quantum Monte Carlo technique to study the two-dimensional Hubbard-Holstein model over a range of fillings, electron-phonon interaction strengths, and phonon frequencies. Previous investigations of the two-dimensional Hubbard model using these techniques have revealed many of the same features as the cuprate superconductors including strong antiferromagnetic correlations and $d$-wave superconductivity. We have modified the QMC algorithm to treat a continuous phonon field and take advantage of the long time scales associated with the phonon dynamics to offset the computational expense associated with sampling the relatively large configuration space. The Maximum Entropy method is employed to calculate the real frequency spectrum which we compare and contrast with recent angle-resolved photoemission (ARPES) experiments. We discuss qualitative and quantitative results in the context of features that seem to be universal to the copper oxides. [Preview Abstract] |
Wednesday, March 7, 2007 10:36AM - 10:48AM |
N9.00014: Intermediate Phase in the Superconducting Cuprates. Takeshi Egami It has long been speculated that upon doping the Mott-Hubbard insulator may go through an intermediate phase before becoming a Fermi-liquid metal. If there is such a phase its structure may be intimately connected to the mechanism of the pseudogap and superconductivity. The only well-defined and popular option has been the spin-charge stripe phase, but the strongly one-dimensional nature of the stripe phase is at odds with the highly two-dimensional CuO$_{2}$ plane. We propose a superlattice of $2\sqrt 2 \times 2\sqrt 2 $ in the $a-b$ plane as an alternative candidate for the intermediate phase. In this phase the Mott-Hubbard states and the Fermi-liquid phase coexist in different Brillouin sub-zones. The presence of such a phase is consistent with the recent results of the ARPES at a high energy scale (J. Graf, \textit{et al.}, \textit{cond-mat/}0607319), dispersion of Cu-O bond-stretching phonon mode in YBCO, pulsed neutron PDF analysis of LSCO, and our recent observation of the supperlattice peaks in YBa$_{2}$Cu$_{4}$O$_{8}$ single crystal by x-ray diffraction. The intensity of the superlattice peaks in YBa$_{2}$Cu$_{4}$O$_{8}$ decreases below 250K. This is an unusual behavior for the ordering peak, suggesting the interplay with superconductivity. [Preview Abstract] |
Wednesday, March 7, 2007 10:48AM - 11:00AM |
N9.00015: Dual character of the electronic structure in YBa$_2$Cu$_4$O$_{8}$: conduction bands of CuO$_2$ planes and CuO chains A. Kaminski, T. Kondo, R. Khasanov, J. Karpinski, S.M. Kazakov, N.D. Zhigadlo, T. Ohta, H.M. Fretwell, A.D. Palczewski, J.D. Koll, J. Mesot, E. Rotenberg, H. Keller We use microprobe Angle-Resolved Photoemission Spectroscopy ($\mu$ARPES) to separately investigate the electronic properties of CuO$_{2}$ planes and CuO chains in the high temperature superconductor, YBa$_2$Cu$_4$O$_{8}$. In the CuO$_2$ planes, a two dimensional (2D) electronic structure with nearly momentum independent bilayer splitting is observed. The splitting energy is 150 meV at ($\pi$,0), almost 50\% larger than in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ and the electron scattering at the Fermi level in the bonding band is about 1.5 times stronger than in the antibonding band. The CuO chains have a quasi one dimensional (1D) electronic structure. We observe two 1D bands separated by $\sim$ 550meV: a conducting band and an insulating band with an energy gap of $\sim$240meV. We find that the conduction electrons are well confined within the planes and chains with a non-trivial hybridization. [Preview Abstract] |
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