Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session B33: Superconductivity: Mostly Cuprates |
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Sponsoring Units: DCMP Chair: Timir Datta, University of South Carolina Room: 403 |
Monday, March 16, 2009 11:15AM - 11:27AM |
B33.00001: Making superconducting transition temperature higher in Bi$_{2}$Sr$_{2}$Ca$_{2}$Cu$_{3}$O$_{10+\delta }$ Xiao-Jia Chen, Viktor V. Struzhkin, Russell J. Hemley, Ho-kwang Mao, Yong Yu, Cheng-Tian Lin We report an experimental finding of \textit{Tc} enhancement in optimally doped Bi$_{2}$Sr$_{2}$Ca$_{2}$Cu$_{3}$O$_{10+\delta }$. We found that the generally observed pressure effect on \textit{Tc}, $i.e.$, \textit{Tc} first increases with pressure and then decreases after passing a maximum at an optimal pressure, is only held below a critical pressure around 24 GPa in this multilayer material. After that \textit{Tc} enhances remarkably upon further compression, considerably surpassing the first maximum. The critical pressure was then considered as the crossover from antiferromagnetism to superconductivity in the inner CuO$_{2}$ plane. The afterwards \textit{Tc} enhancement was suggested through the optimization of two competing energy scales (pairing and phase ordering) of different CuO$_{2}$ planes. The results have important implications for engineering superconductors with much higher \textit{Tc}'s at ambient conditions. [Preview Abstract] |
Monday, March 16, 2009 11:27AM - 11:39AM |
B33.00002: Specific heat of underdoped high $T_c$ superconductors from phenomenological models. J. P. F. LeBlanc, E. J. Nicol, J. P. Carbotte Inspired by phenomenological models for the pseudogap state, for example, the model of Yang, Rice and Zhang[1], we have calculated the specific heat for the underdoped cuprate superconductors. Results will be shown for both the pseudogap and superconducting state as a function of doping. Comparison between models and with experiment will be made. [1] K.Y. Yang, T.M. Rice and F.C. Zhang, Phys. Rev. B 73, 17541 (2006). [Preview Abstract] |
Monday, March 16, 2009 11:39AM - 11:51AM |
B33.00003: Resistive switching in YBa$_2$Cu$_3$O$_{7-\delta}$ Carlos Acha, Marcelo J. Rozenberg We report on the nonvolatile and polarity dependent resistance switching of metal- YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) ceramic superconductor interfaces that also extends macroscopically to the bulk YBCO. We show that electric pulses mainly modify the connectivity of the ceramic grains of the bulk material, affecting the geometrical conducting factor near the interface and controlling the superconducting percolating path in the bulk. Relaxation processes of the resistivity after applying the pulses, not associated with heating effects, are also observed. We also report on the temperature sensitivity of resistance hysteresis switching loops, where both the difference between high and low resistance states and the voltage needed to produce the switching decrease with increasing temperature. The origin of this switching effect may be related to electric field-induced oxygen ion migration, which modifies the oxygen content at grain boundaries and controls the electric transport of ceramic superconductors. [Preview Abstract] |
Monday, March 16, 2009 11:51AM - 12:03PM |
B33.00004: Calculation of diffusion coefficient in Au diffusion-doped Bi$_{1.8}$Pb$_{0.35}$Sr$_{1.9}$Ca$_{2.1}$Cu$_{3}$O$_{y}$ by EDXRF measurements Mustafa Akdogan, Ozgur Ozturk, Ugur Cevik, Ahmet Varilci, Cabir Terzioglu Gold (Au) diffusion in superconducting Bi$_{1.8}$Pb$_{0.35}$Sr$_{1.9}$Ca$_{2.1}$Cu$_{3}$O$_{y}$ was investigated over the temperature range 500-800 \r{ }C by the EDXRF technique. It is found that the Au diffusion coefficient decreases as the diffusion-annealing temperature decreases. The temperature dependences of Au diffusion coefficient in grains and over grain boundaries are described by the relations D$_{1}$=6.7 x 10$^{-5}$exp(-1.19eV/k$_{B}$T) and D$_{2}$=9.7 x 10$^{-4}$exp(-1.09eV/k$_{B}$T), respectively. The diffusion doping of Bi-2223 by Au causes a significant increase of the lattice parameter c by about 0.19{\%}. For the Au-diffused samples, transport measurements indicated the T$_{c}$ increased from 100 to 104K and the J$_{c}$ increased from 40 to 125Acm$^{-2}$, in comparison with those of undoped samples. From SEM and XRD measurements it is observed that Au doping of the sample also improved the surface morphology and increased the ratio of the high-T$_{c}$ phase to the low-T$_{c}$ phase. The possible reasons for the observed improvement due to Au diffusion are also discussed. [Preview Abstract] |
Monday, March 16, 2009 12:03PM - 12:15PM |
B33.00005: Charge distribution on planar oxygens in an underdoped High-Tc cuprate: La(2-x)Sr(x)CuO(4) via $^{17}$O NMR. Greg Boebinger, Robert Smith, Arneil Reyes, Philip Kuhns, Takashi Imai, P. M. Singer, F.C. Chou, K. Hirota, M. Takaba, T. Kakeshita, H. Eisaki , S. Uchida We use high magnetic fields ($\sim $30T) to suppress the superconducting Tc of La(2-x)Sr(x)CuO(4) (LSCO) in order to investigate the normal state NMR properties at low temperatures. We use $^{17}$O NMR as a local probe of the electron density on the planar oxygens. $^{17}$O Knight shift and linewidths were obtained over a wide temperature range in the normal state for under-doped (x=0.05, 0.115) and optimally doped (x=0.15) LSCO. Our results will be discussed in the context of recent reports of charge segregation on the planar oxygens (from STM experiments) and magnetization and neutron scattering experiments showing glassy behavior and incommensurate spin-waves in LSCO. [Preview Abstract] |
Monday, March 16, 2009 12:15PM - 12:27PM |
B33.00006: Magnetic Breakdown in the Cuprates Jean-Michel Carter, Daniel Podolsky, Hae-Young Kee Following the recent observations of quantum oscillations in YBa$_2$Cu$_3$O$_{6.5}$ materials, we study different Fermi surface topologies in order to make a prediction on the nature of the topology of said Fermi surfaces in the cuprates. [Preview Abstract] |
Monday, March 16, 2009 12:27PM - 12:39PM |
B33.00007: Important issues from uncontrolled cation nonstoichiometry in well-known cuprates Jun-ichi Shimoyama, Hiraku Ogino, Shigeru Horii, Yuhya Yamazaki, Koichi Kaku, Yui Ishii, Kohji Kishio Our recent studies revealed that the post-annealing to control cation composition largely changes superconducting properties of cuprate superconductors, such as Bi-based compounds and the RE123 system. For example, the $T_{c}$ of Bi(Pb)2223 was enhanced up to 118 K by post-annealing at $\sim $950 K in air, while it was a typical value of 110 K before post-annealing. Strong correlation between the $c$-axis length and $T_{c}$ suggested that cation composition plays a crucial role to determine superconducting properties of this compound. On the other hand, substitution of RE for Ba-site in RE123 has been well recognized for light-RE123. However, such RE-rich RE123 compounds were found to form even for heavy-RE123 including Y123, which has been considered as a compound free from cation nonstoichiometry. The Y-rich Y123 exhibited suppressed $T_{c}$ down to $\sim $80 K and apparently short $c$-axis length. These result indicated that intrinsic physical properties of layered cuprates should be reexamined after careful control of cation stoichiometry besides control of oxygen composition, because nonstoichiometric cation composition and its local fluctuation strongly affect electronic and vortex systems and related flux pinning properties. [Preview Abstract] |
Monday, March 16, 2009 12:39PM - 12:51PM |
B33.00008: Evidence for nonmonotonic magnetic field penetration in a Pippard superconductor Vladimir Kozhevnikov, Claudiu Giuraniuc, Margriet Van Bael, Kristiaan Temst, Chris Van Haesendonck, Todor Mishonov, Timothy Charlton, Robert Dalgliesh, Yurii Khaidukov, Yurii Nikitenko, Victor Aksenov, Vladimir Gladilin, Vladimir Fomin, Jozef Devreese, Joseph Indekeu Polarized neutron reflectometry (PNR) provides evidence that \textit{nonlocal }electrodynamics governs the magnetic field penetration in an extreme low-\textit{$\kappa $ }superconductor. The sample is an indium film with a large elastic mean free path (11 \textit{$\mu $}m) deposited on a silicon oxide wafer. It is shown that PNR can resolve the difference between the reflected neutron spin asymmetries predicted by the local and nonlocal theories of superconductivity and therefore can be used for direct measurements of the microscopic intrinsic parameters of superconductors. The experimental data support the nonlocal theory, which predicts a \textit{nonmonotonic decay }of the magnetic field. [Preview Abstract] |
Monday, March 16, 2009 12:51PM - 1:03PM |
B33.00009: ABSTRACT WITHDRAWN |
Monday, March 16, 2009 1:03PM - 1:15PM |
B33.00010: Engineering Thin Film Superconductivity toward Single Quantum Channel Limit Shengyong Qin, Jungdae Kim, Qian Niu, Chih-Kang Shih Traditional studies of two-dimensional superconductors were limited to~the regime where the superconducting order parameter behaves as a~two-dimensional wave function but the underline electrons are still three dimensional.~~Recent advancement of materials synthesis have enabled one to grow epitaxial thin superconductor thin films (e.g. Pb) on semiconductor substrates (e.g. Si or Ge) with unprecedented control in crystallinity, atomic smoothness and the layer thickness, thus opening up new opportunities in investigations of two-dimensional superconductivities. Indeed, quantum oscillations of the superconducting order parameter as a function of film thickness have been observed. Moreover, it was found that superconductivity remains very robustness even for films as thin as 5 ML. An interesting question arises as to what extent the robustness of superconductivity remains in even thinner regime. This work presents the case of thin film superconductivity in extreme confinement limit when only one quantum channel is present (i.e. when k$_{F}$L = $\pi )$. [Preview Abstract] |
Monday, March 16, 2009 1:15PM - 1:27PM |
B33.00011: Competition between pairing and magnetic interactions Raimundo dos Santos, Pedro Bertussi, Andre Malvezzi, Thereza Paiva We discuss the interplay between pairing and magnetism by considering a model system composed of both tight-binding electrons and localized moments; the conduction electrons tend to form Cooper pairs due to a local (on-site) attractive interaction, $U$, while they also have a Kondo-like coupling, $J$, with the local moments. Density matrix renormalization group diagonalization on finite one-dimensional lattices (up to 60 sites) is used to calculate magnetic and pairing correlation functions, as well as structure factors in the ground state, in the case of electron density 1/3. Similarly to what happens in the quaternary borocarbides, we find that superconductivity coexists with a variety of magnetic arrangements of the local moments, ranging from commensurate to incommensurate spin-density waves, up to a critical value $J_c(U)$; the conduction electrons show strong antiferromagnetic fluctuations in this region. Superconductivity is then suppressed by the appearance of a magnetic state with broken rotational symmetry in both the local-moment and itinerant electrons subsystems, so that for sufficiently strong $J$, a spiral-ferromagnetic ground state evolves to a ferromagnetic one. [Preview Abstract] |
Monday, March 16, 2009 1:27PM - 1:39PM |
B33.00012: Alpha particle spectrometry using superconducting microcalorimeters Robert Horansky, Joel Ullom, James Beall, Gene Hilton, Gregory Stiehl, Kent Irwin, Alexander Plionis, Stephen Lamont, Clifford Rudy, Michael Rabin Alpha spectrometry is the preferred technique for analyzing trace samples of radioactive material because the alpha particle flux can be significantly higher than the gamma-ray flux from nuclear materials of interest. Traditionally, alpha spectrometry is performed with Si detectors whose resolution is at best 8 keV FWHM. ~Here, we describe the design and operation of a microcalorimeter alpha detector with an energy resolution of 1.06 keV FWHM at 5 MeV. We demonstrate the ability of the microcalorimeter to clearly resolve the alpha particles from Pu-239 and Pu-240, whose ratio differentiates reactor-grade Pu from weapons-grade. We also show the first direct observation of the decay of Po-209 to the ground state of Pb-205 which has traditionally been obscured by a much stronger alpha line 2 keV away. Finally, the 1.06 keV resolution observed for alpha particles is far worse than the 0.12 keV resolution predicted from thermal fluctuations and measurement of gamma-rays. The cause of the resolution degradation may be ion damage in the tin. Hence, alpha particle microcalorimeters may provide a novel tool for studying ion damage and lattice displacement energies in bulk materials. [Preview Abstract] |
Monday, March 16, 2009 1:39PM - 1:51PM |
B33.00013: High Resolution Gamma-Ray Spectroscopy with Superconducting Microcalorimeters D.A. Bennett, J.N. Ullom, W.B. Doriese, J.A. Beall, G.C. Hilton, R.D. Horansky, K.D. Irwin, N. Jethava, E. Sassi, L.R. Vale, M.K. Bacrania, A.S. Hoover, N. Hoteling, P.J. Karpius, M.W. Rabin, C.R. Rudy, D.T. Vo We are currently developing high resolution gamma-ray microcalorimeters (uCal) for improved analysis of nuclear materials. The uCal consist of a bulk superconducting absorber attached to a transition-edge sensor (TES) biased in its resistive transition and operated at temperatures near 0.1 K. Incoming particles and photons are converted to heat in the absorber and the resulting temperature change is measured by the highly sensitive TES thermometer. The unmatched energy resolution of these devices is useful for nuclear safeguards. A specific application is the determination of Pu isotopics in complex mixtures. Although much of our effort is focused on the construction and multiplexed readout of large arrays of detectors for increased collection area, we are also working on optimizing the performance of individual pixels. To this end, we have developed an analytic uCal model that includes the thermal properties of the attached absorber and the large inductance in the TES circuit bias. We show how this model can be used to maximize the number of sensors that can be multiplexed into a single readout channel and to minimize the response time of individual sensors. [Preview Abstract] |
Monday, March 16, 2009 1:51PM - 2:03PM |
B33.00014: In situ measurement of the permittivity of helium using microwave NbN resonators Loren Swenson, Grigorij Grabovskij, Olivier Buisson, Christian Hoffmann, Alessandro Monfardini, Jean-Claude Villegier Due to their high quality-factors and ease of fabrication, superconducting microwave resonators are increasingly being recognized as ideal sensors in ultra-sensitive, low-temperature measurements. In this talk, we will discuss the design and characterization of superconducting NbN quarter-wave resonators implemented as a high-speed and spatially-sensitive detector for the permittivity of a surrounding helium bath. Measurements of a device with a $\sim$10$^{-3}$ mm$^3$ spatial resolution, a $\sim$6$\times$$10^{-11}$ $\epsilon_0$/Hz$^{1/2}$ sensitivity to changes in the permittivity of helium, and a bandwidth of 300 kHz will be presented in the temperature range from 1.8 to 8.8 K. Potential applications, including operation as a fast, localized helium thermometer and as a transducer in superfluid hydrodynamic experiments, will be discussed. [Preview Abstract] |
Monday, March 16, 2009 2:03PM - 2:15PM |
B33.00015: Instabilities and nonlinearities in the elastic vortex solid Satyajit Banerjee, Shyam Mohan, Jaivardhan Sinha, S. Ramakrishnan, A.K. Grover, Ajay Sood In recent times the influence of microscopic disorder has been viewed to play a crucial role in determining the configuration of vortices inside superconductors. Our recent investigations into the dissipation properties of the driven vortices [1], have found the existence of possible symmetry changes deep within the well ordered elastic vortex solid [1]. The result is significant, as it requires a deeper revision of understanding the properties of the so called `benign' elastic vortex solid. We have also studied the nonlinear properties of the driven elastic vortex solid [2] through a random pinning environment and have found interesting highly nonlinear fluctuation in the time domain. We believe our results indicate the presence of process deep within the elastic driven phase which is a precursor to the plastic transformation in the vortex matter. [1] Shyam Mohan, Jaivardhan Sinha, S. S. Banerjee*, and Yuri Myasoedov, Phys. Rev. Lett. 98,027003 (2007). [2] Shyam Mohan, Jaivardhan Sinha, S. S. Banerjee* A. K. Sood, S. Ramakrishna, A. K. Grover (submitted, 2008) \textit{*satyajit@iitk.ac.in} [Preview Abstract] |
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