Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session B25: Superconductivity: Spin properties, Structure and Dynamics |
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Sponsoring Units: DCMP Chair: Young Lee, Massachusetts Institute of Technology Room: D166 |
Monday, March 21, 2011 11:15AM - 11:27AM |
B25.00001: Structure, spin-stripe order, and superconductivity in La$_{1.905}$Ba$_{0.095}$CuO$_4$ with and without 1\% Zn substitution of Cu Jinsheng Wen, Z. Xu, G. Xu, Q. Jie, M. Hucker, A. Zheludev, W. Tian, B. Winn, J. Zarestky, D. Singh, T. Hong, Q. Li, G. Gu, J. Tranquada We have performed susceptibility, thermal transport, and neutron scattering measurements to study the effect of Zn and magnetic field on the structure, spin-stripe order and superconductivity, and the interplay between them in La$_{1.905}$Ba$_{0.095}$CuO$_4$ with and without 1\% Zn. It is shown that the bulk superconductivity is depressed by either the Zn doping or the magnetic field, spin stripe order is enhanced, and the structure is unaffected. For a range of magnetic field, the spin stripe order appears to stabilize a quasi-two-dimensional vortex glass phase. [Preview Abstract] |
Monday, March 21, 2011 11:27AM - 11:39AM |
B25.00002: Electron-Spin Excitation Coupling in an Electron Doped Copper Oxide Superconductor Pr0.88LaCe0.12CuO4-$\delta$ Jun Zhao, Francis C. Niestemski, Shankar Kunwar, Shiliang Li, Paul Steffens, Arno Hiess, Hye Jung Kang, Stephen D. Wilson, Ziqiang Wang, Pengcheng Dai, Vidya Madhavan We use polarized and unpolarized inelastic neutron scattering to study the magnetic excitations of the electron doped copper oxide superconductors Pr0.88LaCe0.12CuO4-$\delta $ (PLCCO, Tc =21 K, 24 K) over a wide energy range. We found the energy dependence of the imaginary part of the dynamic susceptibility displays two distinct energy scales in both samples. Interestingly, the STS measurements on the same samples reveal two modes that evolve with $T_{c}$ in a similar manner as neutron modes. A comparison of the spatial and temperature dependence of the neutron and STS modes suggests that the low energy mode is associated with antiferromagnetism while the high energy mode is connected with superconductivity. These results suggest that spin excitations are the mediating glue for the electron pairing in PLCCO. [Preview Abstract] |
Monday, March 21, 2011 11:39AM - 11:51AM |
B25.00003: Fluctuating stripes at the onset of the pseudogap in the high-Tc superconductor Bi2Sr2CaCu2O8+x Colin Parker, Pegor Aynajian, Eduardo H. da Silva Neto, Aakash Pushp, Shimpei Ono, Jinsheng Wen, Zhijun Xu, Genda Gu, Ali Yazdani A long standing question in high-$T_c$ cuprates has been the interplay between pseudogap, which is generic to all hole-doped cuprates, and stripes, whose static form occurs in only one family of cuprates over a narrow range of the phase diagram. I will present new data [1] on the spatial reorganization of electronic states at the onset of the pseudogap state ($T*$) in the high-temperature superconductor $\textrm{Bi}_2\textrm{Sr}_2\textrm{CaCu}_2\textrm{O}_8+x$ taken with a scanning tunneling microscope (STM). The onset of the pseudogap phase coincides with the appearance of electronic patterns whose doping and energy dependence has the predicted characteristics of fluctuating stripes. While demonstrating that the fluctuating stripes emerge with the onset of the pseudogap state and occur over a large part of the cuprate phase diagram, these experiments indicate that they are a consequence of pseudogap behavior rather than its cause.\\[4pt] [1] C. V. Parker, et al, Nature 2010 (in press) doi:10.1038/nature09597 [Preview Abstract] |
Monday, March 21, 2011 11:51AM - 12:03PM |
B25.00004: Manipulating stripes in La$_{2-x}$Ba$_{x}$CuO$_{4}$ in extreme environments Markus Huecker, Genda Gu, Zhijun Xu, Jinsheng Wen, John M. Tranquada, Martin von Zimmermann Competing magnetic and electronic interactions in the copper-oxide high temperature superconductors often result in nanoscale inhomogeneity of the charge and spin density. Such observations motivated a proposal that dynamic electronic inhomogeneities are intrinsic to the copper-oxide planes, and can result in electronic states that break their four-fold symmetry. We have performed high-energy single-crystal X-ray diffraction in high magnetic fields and at high pressure to show that the charge and spin stripe phase in La$_{2-x}$Ba$_{x}$CuO$_{4}$ constitutes such a state. In particular, our results provide strong evidence that charge stripe correlations in the cuprates are electronically driven and are enhanced within vortices. [Preview Abstract] |
Monday, March 21, 2011 12:03PM - 12:15PM |
B25.00005: Hidden itinerant-spin extreme in heavily-overdoped LSCO revealed by dilute Fe doping: A combined neutron scattering and ARPES study Ruihua He, M. Fujita, M. Enoki, M. Hashimoto, S. Iikubo, S.-K. Mo, H. Yao, T. Adachi, Y. Koike, Z. Hussain, Z.-X. Shen, K. Yamada Fluctuations of the localized spins on Cu and the itinerant spins of doped holes have been theoretically conceived to be both essential for high-Tc superconductivity. While the former clearly leads to an antiferromagnetic order in the undoped Mott phase (the localized-spin extreme), it has remained open whether the latter has an inherent tendency towards the formation of some magnetic order at very high dopings where it becomes dominant (the itinerant-spin extreme). By perturbing the non-magnetically-ordered heavily-overdoped LSCO with 1\% Fe doping, we found by elastic neutron scattering an incommensurate magnetic order induced below 20 K, which cannot be ascribed to the localized spins on Cu or doped Fe. ARPES study of the itinerant doped holes suggests that this order is driven by a strong Fermi surface nesting, which is inherent in the pristine LSCO but has so far eluded a clean revelation. Our finding presents the first experimental example of the long-sought itinerant-spin extreme for cuprates and supports its important fluctuations that should be considered along with its localized counterparts for HTSC at intermediate dopings. [Preview Abstract] |
Monday, March 21, 2011 12:15PM - 12:27PM |
B25.00006: Two distinct electronic sites in the Cu-O plane of the (La, Sr)CuO(4) pseudogap state Robert Smith, Philip Kuhns, Arneil Reyes, Gregory Boebinger At intense magnetic fields (30 T) $^{17}$O NMR exhibits two distinct signatures for planar oxygen sites instead of the singular site expected from the identical lattice symmetry at oxygen sites in the copper-oxygen plane for underdoped, orthorhombic La$_{2- x}$Sr$_{x}$CuO$_{4}$. Analysis of Knight shift, linewidth, quadrupolar splitting and spectral asymmetry indicates that roughly 75$\%$ of the planar oxygens evidence antiferromagnetically- correlated nearest neighbor Cu moments at temperatures below $\sim$30 K, consistent with previous reports. A second planar oxygen site first observed in this study shows that there are mobile holes on roughly 25$\%$ of the planar oxygen sites that (a) suppress magnetism for all T$<$300K and (b) show a Knight shift that drops to zero below $\sim$60 K, evidencing pair formation at a temperature well above the superconducting transition temperature ($\sim$4 K at 30 T) and more than twice the superconducting transition temperature at zero magnetic field. [Preview Abstract] |
Monday, March 21, 2011 12:27PM - 12:39PM |
B25.00007: Oxygen staging in phase separated La2-xSrxCuO4+y Hashini Mohottala, Linda Udby, Samuel Emery, B.O. Wells, J. I. Budnick, Christof Niedermayer, Kim Lefmann, N.H. Anderson, F.C. Chou We studied oxygen staging in a series of La2-xSrxCuO4 (LSCO) samples using neutron scattering. The samples were oxidized using electrochemistry. Electronic phase separation was previously reported in the oxygen rich LSCO system with two stable phases identified as optimally doped superconducting phase and a magnetic phase (1/8th like) with the same ordering temperatures at 40 K [1]. Our present studies show staging in this system. Although staging was observed and extensively studied in the samples with no Sr [2], it has not been reported or systematically studied in the systems with both Sr and oxygen. We do find staging in the oxygenated LSCO system, but the staging peaks evolve as Sr concentration increases and excess oxygen concentration decreases. [1] H Mohottala et al. Nature Materials \textbf{5}, 377 - 382 (2006), [2] B.O. Wells et al., Z. Phys. B 100, 535 (1996). [Preview Abstract] |
Monday, March 21, 2011 12:39PM - 12:51PM |
B25.00008: Tunable High Q Superconducting Microwave Resonator Z. Kim, C.P. Vlahacos, J.E. Hoffman, J.A. Grover, B.K. Cooper, J.R. Anderson, A.J. Dragt, C.J. Lobb, L.A. Orozco, S.L. Rolston, J.M. Taylor, F.C. Wellstood We have developed a frequency tuning system for a ``lumped-element'' thin-film superconducting Nb microwave resonator on sapphire intended for coupling to cold trapped $^{87}$Rb atoms. $^{87}$Rb has hyperfine ground states, $|^{5}S_{1/2},F=1\rangle$ and $|^{5}S_{1/2},F=2\rangle$, which are separated by about 6.83 GHz and available as a two-level system for a qubit. The resonator consists of a meandering inductor and an interdigitated capacitor coupled to a transmission line. At \emph{T}=12 mK and on resonance at 6.863 GHz, the loaded quality factor is 40,000. We employ an Al pin as a frequency tuner by placing it above the inductor using a piezo stage so that one can effectively change the inductance of the resonator. [Preview Abstract] |
Monday, March 21, 2011 12:51PM - 1:03PM |
B25.00009: Nanomechanical Torque Magnetometry of Individual Mesoscopic Superconductors Abdul Suhel, Doug Vick, Mark R. Freeman, John P. Davis We have developed an extremely sensitive form of torque magnetometry based on thin nanomechanical resonators [1]. Previously, we applied this technique to study single magnetic vortices in nanomagnetic samples [2]. One advantage of this technique is that it has good time resolution, and each measurement can be performed quickly enough to gather significant statistics on such events [2]. We are now applying this technique to study single mesoscopic superconducting samples. We intend to measure the magnetic moment associated with superconducting vortices, as well as other magnetic effects that occur in mesoscopic superconductors [3,4]. We will discuss our progress towards this goal. [1] J.P. Davis, et al. Appl. Phys. Lett. \textbf{96}, 072513 (2010). [2] J.P. Davis, et al. New Journal of Physics \textbf{12}, 093033 (2010). [3] A.K. Geim, et al. Nature \textbf{396}, 144 (1998). [4] A.K. Geim, et al. Nature \textbf{407}, 55 (2000). [Preview Abstract] |
Monday, March 21, 2011 1:03PM - 1:15PM |
B25.00010: Strong disorders in cuprate superconductors in d-density wave state Hong-Yi Chen, Chung-Pin Chou The local density of states on strong disordered d-wave superconductor in d-density wave state is studied. Recently, E.W. Hudson et al [Nature Physics 4, 108 (2008) ], reported a method to investigate the pseudogap. We explore the selfconsistent Bogoliubov-de Genns' equations with strong disorders. The quantum interference leading to definitive quasipartical spectra has also been considered. Without d- density wave state, the numerical results are in satisfactory agreement with the observations from STM experiments. With d- densitywave state, a new result can be used to determine the properties of pseudogap. [Preview Abstract] |
Monday, March 21, 2011 1:15PM - 1:27PM |
B25.00011: Resonant Inelastic X-Ray Studies on the Cu-L edge in 1-Dimensional Cuprate Chains James Lee, M. Yi, W.S. Lee, K. Zhou, C. Monney, S. Johnston, J. van den Brink, T. Schmitt, L. Patthey, T.P. Devereaux, K. Kudo, Y. Koike, Z.X. Shen Resonant Inelastic X-ray Scattering (RIXS) is a photon-in, photon-out spectroscopy technique with the capability of seeing many-body interactions in great detail. The recent achievement of sub-eV resolution in RIXS has opened up a new avenue for experiments to study these effects quantitatively. Here we present high-resolution RIXS data at the Cu L-edge on the quasi-one-dimensional edge-sharing chain compound, Ca$_{2+x}$Y$_{2-x}$Cu$_{5}$O$_{10}$, which is the only known dopable quasi-1D chain compound. Charge excitations corresponding to doped holes can be clearly resolved when the photon energy is tuned to the resonance at the hole band. In addition, we find that the d-d excitations appear to disperse with incident photon energy and momentum, and have a nontrivial intensity modulation. Effects of hole doping on these excitations will be discussed. [Preview Abstract] |
Monday, March 21, 2011 1:27PM - 1:39PM |
B25.00012: High-resolution RIXS measurement at O K-edge on the edge-shared chain cuprates, Ca$_{2+x}$Y$_{2-x}$Cu$_{5}$O$_{10}$ W.S. Lee, J. Lee, M. Yi, K. Zhou, S. Johnston, T. Schmitt, Jeroen van den Brink, T.P. Devereaux, K. Kudo, Y. Koike, L. Patthey, Z.X. Shen Quasi one dimensional copper oxides have been model systems in the field of correlated electron physics, because of rich phenomena exhibited in a relatively simple geometry. Its magnetic ground states, fluctuations, and excitations have been investigated extensively by theorists and experimentalists. Among the known quasi 1-D spin-chain compounds, Ca$_{2+x}$Y$_{2-x}$Cu$_{5}$O$_{10}$ is the only compound that can be hole-doped in a wide doping range, providing a unique opportunity to study the dynamics of hole in the quasi-1D environment. Here, we report ultrahigh resolution resonant inelastic soft x-ray scattering experiment at the O K-edge. With an energy resolution of $\sim $50 meV, we resolved rich charge excitations in the sub-eV range that has not been observed in the previous RIXS measurement on the same materials. In particular, we have resolved clear multi-phonon excitations near the elastic peak, suggesting a strong electron-phonon coupling in this quasi-1D system. Doping dependence of these excitations will also be demonstrated. [Preview Abstract] |
Monday, March 21, 2011 1:39PM - 1:51PM |
B25.00013: Suppression of superconductivity in the fully frustrated Josephson junction array with site dilution Bruna de Oliveira, Tommaso Roscilde, Stephan Haas We study the effects of geometric randomness on the ordered phases and phase transitions of frustrated classical Josephson junction (JJ) arrays. In particular, we consider a square lattice array with maximal frustration (one half flux quantum through each plaquette) and with site dilution. The homogeneous model is known to feature two phase transitions: an Ising transition for the ordering of vortices into a crystalline state, and a Kosterlitz-Thouless transition for the appearance of superconductivity. A detailed Monte Carlo study shows a strong effect of disorder on the separation of the ordering temperatures. In particular, superconductivity is completely suppressed well before one reaches the percolation threshold of the lattice. We hence suggest that diluted JJ arrays with magnetic frustration are strong candidates for the experimental observation of a vortex crystal in the normal state. [Preview Abstract] |
Monday, March 21, 2011 1:51PM - 2:03PM |
B25.00014: Dynamical Spectral weight transfer in the cuprates is described by the Hubbard model Philip Phillips, Mark Jarrell Recently, Peets and colleagues [1] measured the x-ray intensity at the oxygen K-edge in overdoped La$_{2-x}$Sr$_x$CuO$_{4\pm\delta}$ (LSCO) and Tl$_2$Ba$_2$CuO$_{6+\delta}$. They concluded that, unlike the underdoped samples of LSCO and YBa$_2$Cu$_3$O$_x$ in which the integrated intensity increases at least linearly with doping, it saturates abruptly for a hole count exceeding $x_c\approx 0.23$. They interpreted the saturation as a breakdown of the 1-band Hubbard model in the cuprates. We analyse all the available data and show that they are completely described by the 1-band Hubbard model. The purported saturation is shown to occur at the doping level at which the dynamical contribution to the spectral weight turns off. \\[4pt] [1] D. C. Peets, Phys. Rev. Lett. {\bf 103}, 087402 (2009). [Preview Abstract] |
Monday, March 21, 2011 2:03PM - 2:15PM |
B25.00015: Superstructure and Magnetism in Na0.825CoO2 - A NMR study P.Y. Chu, B.-L. Young, J.Y. Juang, G.J. Shu, M.-W. Chu, F.C. Chou We report our NMR study of the Na ordering and magnetism in the single crystal of Na0.825CoO2, as follows. 1. The atomic order of Na is observed from the well- resolved 23Na NMR peaks, which suggests 6 Na inequivalent sites. The 59Co NMR also suggests 4 distinct Co sites due to Na ordering. 2. The magnetic field-induced transition from antiferromagnet to ferromagnet is verified by our 23Na spectra at different temperatures and fields. A slow spin dynamic of glassy-like behavior is observed near the AFM and FM boundary. 3. We observed the NMR frequency shift anomaly near 50K, the same temperature where the susceptibility shows the curvature. The anomaly suggests the onset of the magnetic correlation in prior to magnetic ordering. [Preview Abstract] |
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