Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session Q41: Focus Session: Phonons and Electron Correlations in High Tc Superconductors |
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Sponsoring Units: FIAP Chair: David Tanner, University of Florida Room: F152 |
Wednesday, March 17, 2010 11:15AM - 11:27AM |
Q41.00001: Effect of pseudogap formation on the penetration depth of underdoped high $T_c$ cuprates K.A.G. Fisher, E.J. Nicol, J.P. Carbotte, J.P.F. LeBlanc The temperature-dependent penetration depth is calculated over the entire doping range of the cuprate phase diagram with emphasis on the underdoped regime. Pseudogap formation on approaching the Mott transition, for doping below a quantum critical point, is described within the YRZ model [1]. Fermi surface reconstruction is found to have a strong effect on the superfluid density at $T=0$ producing a sharp drop in magnitude, but does not change the slope of the linear low temperature variation. Comparison with recent data on Bi-based cuprates provides validation of the theory and shows that the effects of correlations, captured by Gutzwiller factors, are essential for a qualitative understanding of the data. We compare our results with those for the Fermi arc and the nodal liquid models.\\[4pt] [1] K.Y. Yang, T.M. Rice and F.C. Zhang, Phys. Rev. B 73, 17541 (2006). [Preview Abstract] |
Wednesday, March 17, 2010 11:27AM - 11:39AM |
Q41.00002: ABSTRACT WITHDRAWN |
Wednesday, March 17, 2010 11:39AM - 11:51AM |
Q41.00003: Anisotropic phonon anomaly in Bi2212 manifested by electron-phonon coupling Jiandong Guo, Huajun Qin, Junren Shi, Yanwei Cao, Kehui Wu, Jiandi Zhang, E.W. Plummer, J. Wen, G.D. Gu Electron-phonon coupling (EPC) is one of the important issues in condensed matter physics. Angle-resolved photoemission spectroscopy has been recognized as a powerful tool for the study of EPC by determining the renormalization of electron self energy. For the phonon counterpart, we measure the momentum-dependent phonon spectra of an optimal doped cuprate Bi2212 with high-resolution electron energy loss spectroscopy. The apical oxygen vibration mode at 80 meV exhibits distinct anisotropic anomaly due to EPC. By analyzing the phonon lifetime, the momentum-dependent EPC strength is determined with the knowledge of electron band structure. It is emphasized that the combination of analyses of phonon and electron structures leads to an unambiguous and comprehensive description of EPC. [Preview Abstract] |
Wednesday, March 17, 2010 11:51AM - 12:03PM |
Q41.00004: Exfoliated Thin Crystals: A New Platform For Exploring Cuprate Physics Luke Sandilands, Grigory Chugunov, Shimpei Ono, Philip Kim, Yoichi Ando, Kenneth Burch Electrostatic doping is a promising method for separating the effects of carrier density and disorder in the cuprates. To this end, we have produced exfoliated micro-samples of underdoped Bi-2212 on SiO2/Si substrates. Using this method we reliably produce crystals on the order of hundreds of square microns and as thin as a few unit cells. We present the results of extensive atomic force, optical and polarized Raman microscopy studies of these samples. Taken together these results clearly demonstrate these thin crystals have the same properties as bulk Bi-2212. [Preview Abstract] |
Wednesday, March 17, 2010 12:03PM - 12:15PM |
Q41.00005: Electron-Lattice Contributions to the Cuprate Electronic Structure Seen in Lattice-Strained Bi-2201 Daniel Garcia, J. Graf, C.M. Jozwiak, H. Eisaki, Alessandra Lanzara There is continued interest in how the lattice may relate to the phase diagram in the high temperature superconducting cuprates, particularly on the hole doped side. To explore this effect of the lattice in a controlled way, we performed Angle Resolved Photoemission Spectroscopy on a series of single layered Bi$_{2}$Sr$_{1.6}$Ln$_{0.4}$CuO$_{6+\delta}$ with substituted Lanthanide (Ln= La, Pr, Nd, Eu), with the effect of monotonically decreasing Tc with decreasing Lanthanide atomic radii. We report effects on the electron coupling to bosonic modes near the nodal point as well as effects on near antinodal states with increasing lattice strain. Straddling these regions, we also find additional evidence in the near E$_F$ electronic states for a crossover point in the Brillouin zone we associate with a change in gap function, quasi-particle lifetime, and bosonic coupling of the electronic states. [Preview Abstract] |
Wednesday, March 17, 2010 12:15PM - 12:27PM |
Q41.00006: High-$T_{c}$ Superconductivity meets a 3+3-Dimensional Spectroscopic Tool Jhinhwan Lee, K. Fujita, A. Schmidt, C.K. Kim, H. Eisaki, S. Uchida, J.C. Davis Using a novel high-precision variable-temperature Fourier-transform scanning tunneling spectroscopy (FTSTS) technique, we observed for the first time (Science 325, 1099 (2009)) the complete set of dispersive octet peaks in the pseudogap phase (up to 1.5 $T_{c})$ as well as in the superconducting phase (down to 0.1 $T_{c})$ of the underdoped (UD37K) Bi2212. Looking further into the fine structures of the 3D FTSTS data by a novel cross-sectional analysis technique, we could resolve additional signal components that are key to truly quantitative analyses based on the full many-body Green's function. The high-precision measurement of 3D [2D position(nm), energy(mV)] FTSTS over the entire accessible 3D [T(Kelvin) vs p(doping {\%}) vs B(Tesla)] phase diagram, accompanied by the novel cross-sectional FTSTS analysis based on the full many-body Green's function, will provide one of the most stringent tests for a ``complete'' many-body theoretical understanding of the high-$T_{c}$ cuprate superconductivity. [Preview Abstract] |
Wednesday, March 17, 2010 12:27PM - 12:39PM |
Q41.00007: Modification of RIXS spectra of cuprates due to self energy and matrix element effects Susmita Basak, Tanmoy Das, Hsin Lin, R. Markiewicz, A. Bansil We present a three-band Hubbard Hamiltonian and the associated Cu K-edge resonant inelastic x-ray scattering (RIXS) spectra for electron- and hole-doped cuprates over a wide range of energy and momentum transfers [1]. Intraband and interband excitations across the Fermi energy have been observed in several experiments [2]. We study the doping dependence of the Mott insulator phase transition using RIXS, in particular accounting for the roles of self energy and matrix element effects in modifying the spectra [3]. Work is supported in part by USDOE. \\[4pt] [1] R.S. Markiewicz, A. Bansil, Phys. Rev. Lett. {\bf 96}, 107005 (2006).\\[0pt] [2] Y.W. Li {\it et al.}, Phys. Rev. B {\bf 78}, 073104 (2008).\\[0pt] [3] R.S. Markiewicz {\it et al.}, Phys. Rev. B. {\bf 76}, 174514 (2007). [Preview Abstract] |
Wednesday, March 17, 2010 12:39PM - 12:51PM |
Q41.00008: Doping Dependence of Many-Body Interactions in Cuprate Superconductors with Laser-Based ARPES Christopher Smallwood, Jeff Graf, Christopher Jozwiak, Hiroshi Eisaki, Robert Kaindl, Dung-Hai Lee, Alessandra Lanzara Laser-based technology has opened the field of angle-resolved photoemission to a variety of new techniques. Compared to synchrotron facilities, laser experiments typically benefit from higher flux, greater resolution and bulk sensitivity, and a system that is more readily modified for specialized experiments. We demonstrate the results of using this system to probe bosonic renormalization and electron-electron effects at varied dopings and temperatures in the double-layered cuprate Bi-2212. [Preview Abstract] |
Wednesday, March 17, 2010 12:51PM - 1:03PM |
Q41.00009: Temperature dependence of the nodal quasiparticle in the cuprates high temperature superconductors using laser based angle resolved photoemission Jeff Graf, C. Jozwiak, C. Smallwood, H. Eisaki, R.A. Kaindl, D.-H. Lee, A. Lanzara We used ultra high resolution laser based angle resolved photoemission (ARPES) to study the temperature dependence of the electronic structure of double layer Bi$_{2}$Sr$_{2}$CaCuO$_{8+\delta }$ at optimal doping (Tc=91K) along the nodal direction. Our study reveals fine details of the nodal quasiparticle spectral function as a function of temperature. The results are discussed in terms the electron-lattice and electron-electron interaction in these materials. [Preview Abstract] |
Wednesday, March 17, 2010 1:03PM - 1:39PM |
Q41.00010: Ultra-fast pump-probe determination of electron-phonon coupling in cuprate superconductors Invited Speaker: Fresh femtosecond spectroscopy experiments show the electron-phonon interaction strength $\lambda$ to be 0.7 and 1.4 for YBCO and LSCO respectively and not around 0.2 as previously reported [1]. The revised estimates arise primarily from improved time-resolution, and also partly from improved modeling. Comparison with classical superconductors and pnictides shows non-monotonic correlation of $\lambda$ with $T_c$. Systematic new measurements of the condensate vaporization energy ($U_v$) in cuprates [2] and pnictides reveals a power-law dependence on $T_c$ with exponent 2. However, $U_c$ is 16-18 times greater than the BCS condensation energy $U_c$, implying that a significant heat capacity of the ``bosonic glue.'' In contrast, charge-density wave systems with electronically driven ordering transitions have $U_v \simeq U_c$. The data suggest BCS and Eliashberg-based models to be inappropriate for describing the physics of high-temperature superconductors, and point towards polaron models which consider strong or intermediate $\lambda$.\\[4pt] [1] C.Gadermeier et al., arXiv:0902.1636\\[0pt] [2] P.Kusar et al., Phys. Rev. Lett. 101, 227001 (2008) [Preview Abstract] |
Wednesday, March 17, 2010 1:39PM - 1:51PM |
Q41.00011: Densely mapping the phase diagram of the cuprate superconductor $La_{2-x}Sr_{x}CuO_{4}$ $(0 \leq x \leq 0.18)$, using a spatial composition spread approach Kevin Hewitt, Mehran Saadat, Andrew George Densely mapping the phase diagram of cuprate superconductors is the key to deciphering the normal state properties of these materials. A spatial composition spread approach was used to successfully deposit a 52-member composition spread library of $La_{2-x}Sr_{x}CuO_{4}$ $(0 \leq x \leq 0.18)$. Two home made targets of $La_{2}CuO_{4}$ and $La_{1.82}Sr_{0.18}CuO_{4}$ were sputtered using 41 W RF and 42 W DC bias,respectively, at process gas pressure of 15 mTorr argon. A linear composition variation was produced by using specially designed masks in front of the $La_{2}CuO_{4}$ and $La_{1.82}Sr_{0.18}CuO_{4}$ targets. The libraries were sputtered onto $LaSrAlO_{4}$(001), $SrTiO_{3}$(100) and MgO(100)substrates through a 52-slot shadow mask, and post annealed in a two step sequence - $800^{o}C$ for 1 h then at $950^{o}C$ for 2 h - in a tube sealed with oxygen gas. XRD and WDS analysis revealed the expected doping variation. Resistivity measurements reveal expected features such as a suppression of superconductivity near $\frac{1}{8}$ (x = 0.125) doping and a novel one - that superconductivity appears near 3\% (x=0.03) doping. The work present a powerful approach to studying the phase diagram of existing superconductors as well as offering a method to search for new materials. [Preview Abstract] |
Wednesday, March 17, 2010 1:51PM - 2:03PM |
Q41.00012: Pulsed laser growth and superfluid density measurement of underdoped Bi2Sr2CaCu2O8+x films Jie Yong, Amit Kanigel, Song Wang, Li-Wei Hung, Thomas Lemberger Underdoped Bi2Sr2CaCu2O8+x thins films are made by pulsed laser deposition on MgO and LaAlO3 substrates. By reducing oxygen deposition pressure and postannealing, Tc as low as 6K is achieved. Superfluid density of these films is measured by mutual inductance of a two coil apparatus. Tc is much higher than the one given by 2D Kosterlitz-Thouless-Berezinskii transition temperature calculated for individual CuO2 bilayers. Scaling of Tc with superfluid density will be compared with our previous 2D and 3D YBCO films. [Preview Abstract] |
Wednesday, March 17, 2010 2:03PM - 2:15PM |
Q41.00013: Spin Dynamics and Electron-Phonon Coupling in Cuprates Measured by Resonant Inelastic X-Ray Scattering Jeroen van den Brink, Luuk Ament, Lucio Braicovich, Giacomo Ghiringhelli We show how Resonant Inelastic X-ray Scattering (RIXS) is able to measure not only the dispersion of collective electronic and magnetic excitations in High Tc cuprates [1], but also their coupling to the lattice. At the Cu L$_3$ edge we observe the collective magnetic modes of La$_2$CuO$_4$ (LCO) and underdoped La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) [2,3]. In LCO the single magnon dispersion measured by RIXS coincides with the one determined by inelastic neutron scattering. For LSCO the spin dynamics shows a branch dispersing up to $\sim$400 meV coexisting with a branch at lower energy [3]. Only the latter has been observed with neutrons so far and is considered a key signature of doped cuprates. The presence of the high-energy branch indicates that LSCO is in a dynamic inhomogeneous spin state. RIXS also provides direct, momentum-resolved information on the coupling between electrons and phonons. With it, we determine the e-p coupling strength of the Cu-O breathing mode in La$_2$CuO$_4$ and show that this coupling is strong enough to bring the material close to the polaron self-trapping regime when it is lightly doped with holes. [1] L. Ament {\it et. al.}, PRL 103, 117003 (2009). [2] L. Braicovich {\it et. al.}, PRL 102, 167401 (2009) [3] L. Braicovich {\it et. al.}, ArXiv:0911.0621 (2009). [Preview Abstract] |
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