Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session Y39: Superconductivity-Materials and Processing |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Doug Kirven, Sigma-K Corporation Room: Baltimore Convention Center 342 |
Friday, March 17, 2006 8:00AM - 8:12AM |
Y39.00001: Superconductivity in Yttrium Metal at 17 K James J. Hamlin, Vladimir G. Tissen, James S. Schilling Many of the known elemental superconductors only become superconducting if high pressure is applied. In 1970 J. Wittig [1] discovered superconductivity in yttrium metal at 1.2 K under 11 GPa pressure, $T_{c}$ increasing to 2.7 K at 16 GPa. Using a diamond-anvil cell with dense helium pressure medium, we have extended this pressure range to 89 GPa. We find that $T_{c}$ for yttrium metal reaches values as high as 17 K (ac susceptibility midpoint), one of the highest transition temperatures ever observed for an elemental superconductor. [1] J. Wittig, Phys. Rev. Lett. 24, 812 (1970). [Preview Abstract] |
Friday, March 17, 2006 8:12AM - 8:24AM |
Y39.00002: Synthesis and Characterization of Multilayer Bi(1.6)Pb(0.4)Sr(1.85)Ca(n)Cu(2n+1)O(x) Derrick McRae, Nathaniel Robinson, Jafar Amirzadeh, Ming Yin, Timir Datta A modified solid-state reaction is used to synthesized muli-layer bismuth high Tc superconductor Bi(1.6)Pb(0.4)Sr(1.85)Ca(n)Cu(2n+1)O(x). The number of Ca layers ranged from n=2 to n=9. The resulting ceramic materials were investigated by electron microscopy (SEM) and EDAX. Samples were tested for superconducting transitions. Transport properties were characterized with four-probe method. Influence of synthesis on the temperature dependant behavior of electrical conductivity and superconductivity will be reported. [Preview Abstract] |
Friday, March 17, 2006 8:24AM - 8:36AM |
Y39.00003: Correlation of superconductivity with the apical oxygen ordering . C. Q. Jin, Q. Q. Liu, H. Yang, R.C. Yu, X.M. Qin, L. X. Yang, Y. Yu, F.Y. Li We discuss the evolution of superconducting transition temperature (Tc) with the ordering state at the apical oxygen layer of a high temperature superconductor (HTS). This study became available in Sr$_{2}$CuO$_{3+\delta }$ superconductor with K2NiF4 structure showing so far rarely formed partially occupied apical oxygen which also acts as the dopant. With observation of a series of modulation structures at apical oxygen layer, we found a well-defined links between Tc (from 75 to 95 K) and modulated structures. We address that the distribution geometry of dopant such as the partially occupied apical oxygen here can be an additional route to reach further higher Tc. . [Preview Abstract] |
Friday, March 17, 2006 8:36AM - 8:48AM |
Y39.00004: Oxygen isotope effect in layered cuprate superconductors Xiaojia Chen, Viktor V. Struzhkin, Zhigang Wu, Russell J. Hemley, Ho-kwang Mao, Bing Liang, Clemens Ulrich, Chengtian Lin, Hai-Qing Lin The isotope effect has generally been believed to be important in providing information about the high-temperature superconductivity. We report systematic studies of the oxygen isotope effect in nearly optimally doped Bi$_{2}$Sr$_{2}$Ca$_{n-1}$Cu$_{n}$O$_{2n+4+\delta }$ (n=1,2,3) single crystals. We find that $\alpha $ decreases monotonically with increasing the number of CuO$_{2}$ layers in this series, which is considered as a result of the interlayer coupling effect. Our results suggest that a $d$-wave BCS equation with a phonon cutoff is able to provide a self-consistent explanation for both the Tc and $\alpha $ behaviors of cuprates covering the parameters of doping, CuO$_{2}$ layer, and compound. The proposed theoretical model is also used to predict the pressure dependence of the oxygen isotope exponent in the optimally doped YBa$_{2}$Cu$_{3}$O$_{7-\delta }$ based on our measured Tc and Raman data. We find that $\alpha $ decreases with increasing pressure and becomes negative at some pressure. Such prediction is waiting for direct isotope measurements under high pressures. [Preview Abstract] |
Friday, March 17, 2006 8:48AM - 9:00AM |
Y39.00005: The effect of process gas pressure, target composition, Ar:O$_{2}$ ratio and substrate bias on the preparation of thin films of the superconductor Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$ Robert J. Sanderson, Kevin C. Hewitt Thin films prepared by DC magnetron sputtering of single targets of the well known superconductor Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta }$ and an enriched target of composition Bi$_{2.2}$Sr$_{2}$Ca$_{1.1}$Cu$_{2}$O$_{8+\delta }$ were studied to determine the effect of deposition conditions on the resulting film. The targets were both sputtered at a power of 60 Watts for 83.3 minutes, at a base pressure of (5$\pm $1)x10$^{-7}$ Torr. Films were deposited onto Al foil using a comprehensive range of deposition pressures (3.96 to 27.3 mTorr), Ar:O$_{2}$ gas ratios (1:1, 1:2, 1:3 and 2:1) and substrate biases (-5, -20, and -30 V). Elemental analysis using energy dispersive spectroscopy allows us to determine the effect of these variables on each individual element in the deposited film. The proportion of Bi increases linearly with increasing process gas pressure. Changing the Ar:O$_{2}$ ratio does not have a major effect on the composition, but it does slightly vary the Sr and Ca concentrations. Resputtering was present in the film which had a -5 V bias, the -30 V bias also showed a reduced elemental composition, while the -20 V bias produced the best composition. The results of this study show the fickle nature of depositing films from multi-element oxide targets, and the need to optimize conditions to produce the desired film. [Preview Abstract] |
Friday, March 17, 2006 9:00AM - 9:12AM |
Y39.00006: Large Single Crystal growth of Bi-2212 superconducting oxide Genda Gu, Gangyong Xu, John Tranquada A floating zone method was used to study the effects of the growth velocity and starting composition of the feed rod on the crystal growth behaviour of Bi-2212 superconducting materials. It shows that a necessary condition for large single crystal growth is that the solid-liquid interface of a rod maintains a planar interface during crystal growth. The planar solid-liquid interface tends to break down into the cellular interface while increasing the velocity from 0.3 mm/h, or while deviating from the optimum starting composition of the feed rod Bi$_{2.1}$Sr$_{1.9}$Ca$_{1.0}$Cu$_{2.0}$O$_{x}$. The single crystals up to 100$_{\ast }$7$_{\ast }$3.8 mm$^{3 }$along the $a$-, the $b$- and the $c$-axis have been grown in a \textit{$\Phi $}7mm rod with optimum growth conditions. The single crystals of up to 50*7*3.8 mm$^{3}$ have been picked up from the cut section of the as-grown rod. The neutron measurements show that the quality of the single crystals is good. The superconducting transition temperature $Tc_{onset}$ by SQUID is 91K for as-grown crystals. [Preview Abstract] |
Friday, March 17, 2006 9:12AM - 9:24AM |
Y39.00007: A Search for Novel Superconductors: A Study of the Lithium-Boron System Michael Bleiweiss, Jafar Amirzadeh, Ming Yin, Douglas Kirven, Ed Sharp, Timir Datta A rapid solid-state reaction was used to synthesize a class of novel lithium-boron based ceramics. The resulting multiphase ceramic materials were investigated by XRD, electron microscopy (SEM) and EDAX. Efforts were taken to avoid contamination by magnesium diboride; MgB$_{2}$ was not detectable by XRD or EDAX. A number of the samples were electrically conducting and some were found to be superconducting in the 30-40 K range. Superconducting transitions were confirmed by SQUID magnetometry. Efforts are in progress to identify and isolate the superconducting phase. Influence of preparation on the electrical conductivity and superconductivity will be reported. [Preview Abstract] |
Friday, March 17, 2006 9:24AM - 9:36AM |
Y39.00008: A Novel Method to Detect Oxygen Vacancies in the Grain Boundaries of High-Tc Superconductors Takahiro Tomita, James S. Schilling, Lihua Chen, Boyd W. Veal, Helmut Claus A new diagnostic method is introduced (pressure-induced $J_{c}$ relaxation) which is capable of detecting oxygen vacancies in the grain boundaries of oxide superconductors. A series of bicrystalline rings of YBa$_{2}$Cu$_{3}$O$_{x}$ containing single [001]-tilt grain boundaries with mismatch angles from 0 to 31 degrees are studied. Even for samples with nearly optimal doping in the bulk, a significant oxygen deficiency in the grain boundary region is revealed. In addition, compressing the grain boundary region is found to lead to a considerable enhancement of the critical current density $J_{c}$. [Preview Abstract] |
Friday, March 17, 2006 9:36AM - 9:48AM |
Y39.00009: Crystal Growth and Electrical Transport Properties of Low Dimensional Nb-Se Superconducting Phases Cedomir Petrovic, Rongwei Hu, Vesna Mitrovic Single crystals of NbSe$_{2}$ and Nb$_{2}$Se$_{3}$ have been grown by molten metallic flux technique. Powder x-ray diffraction confirms phase purity. Superconducting transitions have been observed for both materials. Electronic transport properties and comparison with samples made with conventional chemical vapor transport method will be discussed. [Preview Abstract] |
Friday, March 17, 2006 9:48AM - 10:00AM |
Y39.00010: Epitaxial thin films of the superconducting spinel oxide LiTi$_{2}$O$_{4}$ Rajesh Chopdekar, Yuri Suzuki Lithium titanate is the only superconducting spinel oxide documented in literature. Related oxide spinels[1] such as the heavy fermion system LiV$_{2}$O$_{4}$ and charge-ordered LiMn$_{2}$O$_{4}$ indicate that electron correlations are strong in these systems. We have fabricated epitaxial films of LiTi$_{2}$O$_{4}$ on MgAl$_{2}$O$_{4}$ and MgO single crystalline substrates to explore such behavior in thin film form. Atomic force microscopy indicates $<$1nm RMS surface roughness, and 2- and 4-circle x-ray diffraction confirms film epitaxy. Films on MgAl$_{2}$O$_{4}$ have a critical temperature T$_{c}$ of up to 11.3K with a resistivity transition width of 0.25K, while films on MgO have lower T$_{c}$ with broader transitions. Magnetization vs. magnetic field of a zero-field cooled sample shows Meissner shielding consistent with Type II superconductors. Such films can be used in spin-polarization measurements of complex oxide half-metallic thin films, as well as fundamental studies of the effect of epitaxial strain, microstructure, and cation disorder/substitution on the superconducting properties of LiTi$_{2}$O$_{4}$. [1] M. Lauer et al, Phys Rev B 69, 075117 (2004). [Preview Abstract] |
Friday, March 17, 2006 10:00AM - 10:12AM |
Y39.00011: The annealing process and its relationship to superconductivity in the electron-doped superconductors Hye Jung Kang, Pengcheng Dai, Branton Campbell, Stephan Rosenkranz, Peter Chupus, Shiliang Li, Y. Kurita, Seiki Komiya, Yoichi Ando Superconductivity in the high transition temperature superconductors can be achieved when the antiferromagnetic insulating parent compounds are doped with holes or electrons. The discovery of the electron-doped superconductors has obtained special attention because of the symmetry with doped charge carriers. The electron-doped superconductors can provide important clues in the mechanism of high temperature superconductivity by finding fundamental features seen in the hole-doped superconductors. Unlike hole-doped superconductors, the electron-doped compounds require the annealing process to achieve superconductivity. The role and effects of the annealing process on superconductivity have been one of the unresolved problems in the electron-doped superconductors. To investigate how the annealing process is associated to superconductivity, we performed X-ray measurement on an as-grown, an annealed superconducting, an oxygenated nonsuperconducting, and a reannealed Pr0.88LaCe0.12CuO4 samples. [Preview Abstract] |
Friday, March 17, 2006 10:12AM - 10:24AM |
Y39.00012: Pressure Dependence Transport Studies of the Possible Charge Kondo Effect in Tl-doped PbTe Yosuke Kurosaki, Jun Shinagawa, Yana Matsushita, Ted Geballe, Ian Fisher, Stuart Brown Pb$_{1-x}$Tl$_x$Te is noteworthy for a high superconducting transition temperature relative to carrier concentration, as well as normal state properties consistent with a charge-Kondo effect. Recent experiments also demonstrate that the onset of an observable superconducting T$_c$ with Tl concentration at x$\sim$0.3\% coincides with features characteristic of charge Kondo [1], including d$\rho$/dT$<$0 at low temperatures and an unusual linear variation of the resistivity $\rho(T)$=$\rho_0 $+AT at higher temperatures. Together, these observations are consistent with an association between the two phenomena [2]. We report the effect of applied pressures up to P$\sim1.5$GPa on $\rho(T)$, T$_c$, and the Hall number p$_H\equiv$R$_H^{-1}$ for x= 0.3\%, 0.8\%, and 1.3\%. T$_c$ is reduced sharply with pressure, dT$_c$/dP=400-500mK/GPa as the low temperature Kondo- like upturn in $\rho(T)$ is weakened. Also, dA/dP$<$0 and dp$_H$/dP$>$0. These observations are discussed in the context of the proposed charge-Kondo model for Pb$_{1-x}$Tl$_x$Te. [1] Y. Matsushita, H. Bluhm, T.H. Geballe and I.R. Fisher, Phys.Rev.Lett. 94, 157002(2005).[2] M. Dzero and J. Schmalian, Phys.Rev.Lett. 94, 157003 (2005). This work is supported by NSF frant DMR-0520552. [Preview Abstract] |
Friday, March 17, 2006 10:24AM - 10:36AM |
Y39.00013: Superconductivity and anomalous transport in PbTe:Tl Elihu Abrahams, Piers Coleman, Maxim Dzero, Joerg Schmalian We analyze the transport properties of Tl-doped PbTe. We show that upon doping, Tl has degenerate valence states 1+ and 3+. Quantum valence fluctuations lead to the superconductivity and a charge Kondo effect at low-temperatures and cause linear temperature dependence of resistivity at high temperatures. [Preview Abstract] |
Friday, March 17, 2006 10:36AM - 10:48AM |
Y39.00014: Superconducting Properties of Tl-Doped PbTe Y. Matsushita, P. A. Wianecki, T. H. Geballe, I. R. Fisher, R. J. Ormeno, P. J. Baker, C. E. Gough Tl-doped PbTe (Pb$_{1-x}$Tl$_x$Te) has a remarkably high $T_c$ given its relatively low carrier concentration and also exhibits unusual electronic properties [1--2]. For Tl concentrations $x$ beyond a critical value $x_c \sim 0.3\%$, it is observed to superconduct with $T_c$ rapidly increasing with $x$ up to a maximum doping of 1.5$\%$ and a maximum $T_c$ of 1.5 K. Here we present results of heat capacity, transport, and microwave conductivity experiments for single crystal samples. We extract estimates of superconducting parameters including $\Delta C/ \gamma T_c$, $H_{c2}$, coherence length, and penetration depth. For the highest Tl concentrations, we find that the heat capacity anomaly and the temperature dependence of the superfluid density are consistent with BCS predictions and that the material is in the dirty limit. [1] Y. Matsushita, H. Bluhm, T.~H. Geballe, and I.~R. Fisher, Phys. Rev. Lett. \textbf {94}, 157002 (2005). [2] M. Dzero and J. Schmalian, Phys. Rev. Lett. \textbf{94}, 157003 (2005). [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700