Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session P12: Superconducting Materials |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Myron Salamon, University of Illinois Room: LACC 402A |
Wednesday, March 23, 2005 11:15AM - 11:27AM |
P12.00001: Structure and Physical Properties of Hydrated Sodium Cobalt Goran Gasparovic, R.A. Ott, B. Khaykovich, F.C. Chou, E.T. Abel, J.W. Lynn, S.E. Nagler, J.P. Hill, K.J. Thomas, Y.S. Lee Using an electrochemical de-intercalation technique, we have produced single crystal samples of hydrated sodium cobalt oxide (Na$_{0.3}$CoO$_{2}\cdot$1.3H$_{2}$O). Thermodynamic and transport measurements reveal the low temperature properties of these samples to be consistent with those of a Fermi liquid with a strong mass enhancement. We have used neutron scattering and x-ray scattering to study the structure and excitations of this compound. We find that there are multiple stable structures which differ in the stacking arrangement of the planes. We discuss the bulk physical properties of the various compositions measured. [Preview Abstract] |
Wednesday, March 23, 2005 11:27AM - 11:39AM |
P12.00002: Revised superconducting phase diagram of hole doped Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O C.J. Milne, D.N. Argyriou, A. Chemseddine, N. Aliouane, J. Veira, S. Landsgesell, D. Alber We have studied the superconducting phase diagram of Na$_{x}$CoO$_{2}\cdot y$H$_{2}$O\space as a function of electronic doping, characterizing our samples both in terms of Na content $x$ and the Co valence state.[1] Our findings are consistent with a recent report that intercalation of H$_{3}$O$^{+}$\space ions into Na$_{x}$CoO$_{2}$, together with water, act as an additional dopant indicating that Na sub-stochiometry alone does not control the electronic doping of these materials. We find a superconducting phase diagram where optimal T$_{c}$\space is achieved through a Co valence range of 3.24 - 3.35, while T$_{c}$\space decreases for materials with a higher Co valence. The critical role of dimensionality in achieving superconductivity is highlighted by similarly doped non-superconducting anhydrous samples, differing from the superconducting hydrate only in inter-layer spacing. The increase of the interlayer separation between CoO$_{2}$ sheets as Co valence is varied into the optimal T$_{c}$\space region is further evidence for this criticality.[1] C.J. Milne $et al.$, $Phys. Rev. Lett.$, in press (2004). Also cond-mat/0401273. [Preview Abstract] |
Wednesday, March 23, 2005 11:39AM - 11:51AM |
P12.00003: Evidence of two-gap superconductivity in Na$_{0.35}$CoO$_2\cdot$1.3H$_2$O H. Q. Yuan, M. B. Salamon, D. Vandervelde, P. Badica, K. Togano , K. Yamada The recent discovery of superconductivity in the layered cobalt oxyhydrate Na$_{0.35}$CoO$_2\cdot$1.3H$_2$O [1] has attracted considerable attention in the scientific community because of its structural similarity to high-T$_c$ cuprates. Although intensive studies have been performed to understand the nature of superconductivity in this compound, no consensus has been reached on many important issues and the symmetry of order parameter still remains open. The low temperature behavior of the magnetic penetration depth $\lambda(T)$ provides a useful probe of the low-lying excitations in superconductors and hence of the symmetry of the superconducting energy gap. In this contribution, we present a high-precision measurement of $\lambda(T)$ on singe crystalline Na$_{0.35}$CoO$_2\cdot$1.3H$_2$O down to 90 mK, using a tunnel-diode based, self-inductive technique at 21 MHz. It is found that $\lambda(T)$ can be fit by a quadratic power-law above $T\simeq 1$ K. However, $\lambda(T)$ changes to an exponential decay at the lowest temperature ($T < 0.8$ K), indicating that the material is fully gapped. Detailed analysis shows that $\lambda(T)$ can be nicely fitted with a two-band model, resembling the case of MgB$_2$. These findings are consistent with the recent report of specific heat results [2] and suggest s-wave superconductivity in Na$_{0.35}$CoO$_2\cdot$1.3H$_2$O. [1] K. Takada et al, Nature \bf{53} (2003). [2] R. Jin et al, cond-mat 0410517. [Preview Abstract] |
Wednesday, March 23, 2005 11:51AM - 12:03PM |
P12.00004: High Pressure Structure of Na$_{0.75}$CoO$_2$ Ravhi Kumar, Andrew Cornelius, Malcolm Nicol, D Prabhakaran, Andrew Boothroyd, Maddury Somayazulu High pressure x-ray diffraction experiments were performed on Na$_{0.75}$CoO$_{2}$, using synchrotron x-rays and dimond anvil cell up to 25 GPa, at ambient and cryogenic temperatures down to 10 K. The hexagonal structure of this compound is found to be stable at both conditions, and no structural changes were found around the unconventional magnetic state reported at 22 K. The bulk modulus obtained at ambient temperature, by fitting the pressure volume (PV) data shows, the compound is less compressible than its hydrated analogues. A rapid decrease observed in the c/a ratio under pressure, at ambient and low temperatures, indicates the presence of strong lattice anisotropy in this system similar to the high T$_{c}$ cuprates. [Preview Abstract] |
Wednesday, March 23, 2005 12:03PM - 12:15PM |
P12.00005: Pulsed Laser Deposition of Na$_x$CoO$_2$ Thin Films Weidong Si, Sangmoon Park Na$_{x}$CoO$_{2}$ has been discovered to have very large thermoelectric power, which shows that it may be used in potential integrated heating spreading solution. Recently it was also found to be superconducting at certain sodium concentration after intercalated with water. It has a layered structure similar to the cuprates and considered to be helpful to the understanding of the mechanism of the high temperature superconductor. We have successfully grown c-axis oriented thin films of Na$_{x}$CoO$_{2}$ on substrates of polycrystalline sapphire and (0001) sapphire by pulsed laser deposition. The in-plane transport and magnetic measurements has been performed in the Na$_{x}$CoO$_{2}$ films and show similar behaviors as in the single crystal samples. Their structure properties as well as physical properties will be discussed. [Preview Abstract] |
Wednesday, March 23, 2005 12:15PM - 12:27PM |
P12.00006: Effects of Disorder on the Normal State of Pr$_{2-x}$Ce$_{x}$CuO$_{4-\delta}$ J.S. Higgins, Y. Dagan, M.C. Barr, R.L. Greene, B.D. Weaver We present a study on epitaxial thin films of the electron-doped superconducting cuprate Pr$_{2-x}$Ce$_{x}$CuO$_{4-\delta }$ (PCCO) as a function of disorder and oxygen content. Overdoped samples (x = 0.17, 0.19) were made using a pulsed laser deposition technique. Oxygen content was adjusted during the annealing process and disorder was induced by proton irradiation. The evolution of the resistivity and the Hall coefficient is examined, with a focus placed on the normal state properties in the regime T $<$ T$_{c}$ and H $>$ H$_{c2}$. Results are compared between optimally prepared, oxygenated, and irradiated samples. [Preview Abstract] |
Wednesday, March 23, 2005 12:27PM - 12:39PM |
P12.00007: Superstructural lattice distortion within electron doped superconductor Pr$_{0.88}$LaCe$_{0.12}$CuO$_{4}$ Branton J. Campbell, Stephan Rosenkranz, Peter J. Chupas, Hye Jung Kang, Pengcheng Dai, Yasuaki Kurita, Seiki Komiya, Yoichi Ando It is well-known that electron-doped Nd$_{0.85}$Ce$_{0.15}$CuO$_{4}$ can be reversibly converted between the superconductor and non-superconductor by appropriate high-temperature treatments in reducing or oxidizing environments, respectively. Samples that exhibit superconductivity also present a crystalline Nd$_{2}$O$_{3}$ (bixbyite structure) impurity phase as well as diffuse (0, 0, L) rods of scattering at superlattice positions in the (H, K, 0) plane that coincide with the reciprocal lattice of the larger 2$\surd $2 $\times $ 2$\surd $2 impurity cell. We present a diffuse scattering analysis of the rod scattering in related compound Pr$_{0.88}$LaCe$_{0.12}$CuO$_{4}$ (PLCCO) and demonstrate that they are evidence of a superstructural distortion of the CuO$_{2}$ sheets, rather than an impurity effect. This in-plane superstructure may prove to be a necessary condition for superconductivity in the electron-doped cuprates. [Preview Abstract] |
Wednesday, March 23, 2005 12:39PM - 12:51PM |
P12.00008: The effect of annealing to the transport and magnetic properties of electron-doped Pr$_{0.88}$LaCe$_{0.12}$CuO$_{4}$ Shiliang Li, Stephen Wilson, Songxue Chi, Pengcheng Dai, Seiki Komiya, Yoichi Ando The single crystals of electron doped cuprate Pr$_{0.88}$LaCe$_{0.12}$CuO$_{4+\delta}$ have been grown by floating-zone method. As-grown, the samples exhibit long-range antiferromagnetic order without superconductivity. Superconductivity only appears after annealing the sample in pure Ar or vacuum. We present a detailed investigation on how annealing conditions affect the in-plane and $c$-axis resistivity and hall coefficients. We will also discuss the chemical compositions of these samples before and after annealing. [Preview Abstract] |
Wednesday, March 23, 2005 12:51PM - 1:03PM |
P12.00009: Thin Film Growth via Pulsed Laser Deposition and Characterization of the Electron-Doped Superconductor Sm$_{2-x}$Ce$_x$CuO$_{4-y}$ D. J. Scanderbeg, B. J. Taylor, Y. Kim, M. B. Maple We report the growth and characterization of the electron-doped superconductor Sm$_{2-x}$Ce$_x$CuO$_{4-y}$ (SCCO). The growth conditions and in-situ annealing procedures for the thin films grown on yttria-stabilized zirconia (YSZ) substrates have been established. These are reported along with x-ray diffraction measurements, magnetic susceptibility, and magnetoresistance R(H, T) data. Scaling analysis of the transport measurements yields a diagram of the vortex-glass melting line. The films have a superconducting transition temperature as high as T$_c$ = 17.8 K and a transition width $\Delta$T$_c$ = 0.93 K. A comparison between our results on thin films and those on single crystals is also made. The results from additional underdoped (x $<$ 0.15) and overdoped (x $>$ 0.15) concentrations are also presented. High magnetic field and low temperature data were taken at the National High Magnetic Field Laboratory (NHMFL) in Tallahassee, Florida. This research was supported by the US Department of Energy under Grant No. FG03-86ER-45230 and the CULAR program no. 9985-001. [Preview Abstract] |
Wednesday, March 23, 2005 1:03PM - 1:15PM |
P12.00010: Origin of superconducting carriers in ``non-doped'' T$^{\prime}$-(La, RE)$_{2}$CuO$_{4}$ (RE = Sm, Eu, Gd, Tb, Lu, and Y) Hideki Yamamoto, Akio Tsukada, Masumi Noda, Michio Naito We have reported the isovalently-substituted new superconductors T'-La$_{2-x}$\textit{RE}$_{x}$CuO$_{4}$ ($T_{c}\sim $20-25K) prepared by MBE with no effective dopant. As regards the origin of the carriers in these nominally non-doped superconductors, there seems to be two possible scenarios: (i) oxygen deficiencies at the regular oxygen sites serve as a source of effective electron carriers, and (ii) they are not Mott insulators and have intrinsic carriers. Since precise information on the site- specific occupancy of oxygen is very difficult to obtain, alternatively, we investigated the in-plane lattice constant $a_{0}$ with changing \textit{RE} concentration $x$, with a view to examining possible $a_{0}$ expansion due to electron doping. In each \textit{RE} substitution, the $a_{0 }$of the T'-La$_{2-x}$\textit{RE}$_{x} $CuO$_{4 }$linearly decreases with increasing $x$, whose extrapolation to $x$=2 agrees well with the reported value for bulk T'-\textit{RE}$_{2}$CuO$_{4}$. This$_{ } $variation can simply be understood based on the difference in the ionic radius of \textit{RE}$^{3+ }$vs La$^{3+}$, suggesting that these superconductors$_{ }$are not electron-doped, at least substantially, and that the second scenario is the more plausible. This conclusion is also supported by the results of transport and photoemission experiments. [Preview Abstract] |
Wednesday, March 23, 2005 1:15PM - 1:27PM |
P12.00011: Electric-field-induced modulation of the magnetic penetration depth of superconducting La$_{2-x}$Sr$_{x}$CuO$_{4}$ ultrathin films A. Ruefenacht, P. Martinoli, J. Fompeyrine, D. Caimi, J.-P. Locquet A study of the electric-field-induced change of the in-plane magnetic penetration depth $\lambda _{ab}$ of an underdoped La$_{2-x}$Sr$_{x}$CuO$_{4}$ (LSCO) ultrathin superconducting (S) film is reported for the first time. Using MBE, a two unit-cell (UC) thick (x$\approx $0.1) LSCO S-film was grown epitaxially on a 12 UC thick normal (x=0.4) LSCO buffer layer deposited on a monocrystalline. SrLaAlO$_{4}$ substrate. A capacitor structure was then patterned after growing on top of the S-film a 15 nm thick HfO$_{2}$ insulating layer with a dielectric constant $\varepsilon \approx $15 and a Pt gate electrode. The inverse kinetic inductance 1/L$_{k}\propto $ 1/$\lambda _{ab}^{2}$ of the LSCO film was measured using an inductive two-coil technique. Both the temperature (T) and magnetic-field dependences of 1/L$_{k}$ were investigated by applying gate voltages corresponding to electric fields E = $\pm $ (2 x 10$^{8})$ V/m. For the largest E-field modulation ($\Delta $E $\equiv $ 4 x 10$^{8}$ V/m) a relative change $\Delta $L$_{k}^{-1}$/L$_{k}^{-1}\approx $ 18{\%} was observed at low temperature in good agreement with an elementary theoretical estimate. The nonmonotonic T-dependence of $\Delta $L$_{k}^{-1}$/L$_{k}^{-1}$ (a maximum is observed where L$_{k}^{-1}$(T) has the largest slope) can be accurately described by a simple model assuming that L$_{k}^{-1}$(0) $\propto $ T$_{c}$. [Preview Abstract] |
Wednesday, March 23, 2005 1:27PM - 1:39PM |
P12.00012: Experimental observation of magic doping fractions and two-dimensional charge ordering in La$_{2-x}$Sr$_x$CuO$_4$ Seiki Komiya, H.-D. Chen, S.-C. Zhang, Yoichi Ando Competing order is currently an issue of controversy in the study of high temperature superconductivity. In LSCO, neutron scattering experiments have found one-dimensional spin stripes; however, it is unclear whether LSCO has some sort of charge-ordered state. If there is a charge-ordered state in LSCO, the charge ordering tendency is expected to be pronounced near certain doping levels where the charge modulation is commensurate with the underlying lattice; therefore, to examine the nature of possible charge ordering in LSCO, we have carefully measured the hole-doping dependence of the in-plane resistivity using a series of high-quality single crystals. Our detailed measurements find a tendency toward charge ordering at particular rational hole doping fractions of 1/16, 3/32, 1/8, and 3/16. This observation is most consistent with a recent theoretical prediction of the checkerboard-type ordering of the Cooper pairs at rational doping fractions $x=(2m+1)/2^n$, with integers $m$ and $n$. [Preview Abstract] |
Wednesday, March 23, 2005 1:39PM - 1:51PM |
P12.00013: Synthesis and Charateriztion of BSCCO System Doped with Ru, Nb and Ho Fouzi Arammash, Brett McCarty, Ruslan Prozorov Samples of Bi$_{2}$Sr$_{2}$CaCu$_{2-x}$ A$_{x}$O$_{8}$ with A=Ru, Nb, Ho and X=0.0, 0.10, 0.15, 0.2 were synthesized using ammonium nitrate melt method. Appropriate amounts of Bi$_{2}$O$_{3}$, SrCO$_{3}$, and the oxides of the doping elements, etc were mixed together. A small amount of ammonium nitrate was added to the mixture and reground thoroughly using an agate mortar and a pestle. The resulted precursor then heated between 160-170C under hood. Further heating at 400-500 C resulted in the formation of dark colored powder. The powder was then pressed into small pellets and annealed at 950 C in flowing oxygen for 24 hours and then furnace cooled to room temperature. The samples were characterized by measuring their magnetic as well as superconducting properties which will be presented. [Preview Abstract] |
Wednesday, March 23, 2005 1:51PM - 2:03PM |
P12.00014: Growth and characterization of large HgBa$_{2}$CuO$_{4+\delta}$ single crystals Guichuan Yu, Xudong Zhao, Li Lu, Guillaume Chabot-Couture, Martin Greven Using flux techniques, we have been able to grow unprecedentedly large HgBa$_{2}$CuO$_{4+\delta}$ (Hg1201) single crystal, exceeding 20 mm$^{3}$ in volume. Hg1201 is a model high-temperature superconductor, with the highest T$_c$ ($\sim 97$ K at optimal doping) among all single-layer cuprates and a simple tetragonal crystal structure. X-Ray and neutron scattering measurements demonstrate the single-grain nature of our crystals. We report results for the uniform susceptibility and the resistivity. Measurements of the $c$-axis resistivity and magnetoresistance were used to determine the pseudogap temperature at several hole densities. [Preview Abstract] |
Wednesday, March 23, 2005 2:03PM - 2:15PM |
P12.00015: Growth and superconductivity of single crystals La$_{1.875}$Ba$_{0.125}$CuO$_4$ Genda Gu, Guangyong Xu, J. Tranquada, Q. Li, A. Moodenbaugh, H. Goka, K. Yamada The origin of high temperature superconductivity in cuprate materials is one of the biggest puzzles in material science. Since the discovery of the significant anomalous suppression of superconductivity in high temperature superconducting oxide La$_{2-x}$Ba$_{x}$CuO$_{4 }$(x=1/8) $^{[1]}$, the so-called 1/8 anomaly has been a subject of considerable research attention. Many attempts to grow the single crystals have been made, but no single crystal La$_{2-x}$Ba$_{x}$CuO$_{4 }$(x=1/8) has been successfully grown. In this work, the effects of the growth condition and the compositions of a feed rod on the crystal growth of La$_{2-x}$Ba$_{x}$CuO$_{4 }$has been studied by an infrared image floating zone method. The experimental result shows that a planar solid-liquid growing interface tends to break down into a cellular interface when the growth velocity is more than 1 mm/h. When the planar solid-liquid growing interface break down into a cellular interface, the single crystal size decreases abruptly and the as-grown rod is not single phase. The large single crystals of La$_{2-x}$Ba$_{x}$CuO$_{4 }$(x=1/8) has been successfully grown. The single crystals of La$_{2-x}$Ba$_{x}$CuO$_{4 }$(x=1/8) up to 8 mm diameter and 55 mm length have been cut from the as-grown bars. The superconductivity transition temperature T$_{c}$ of as-grown single crystals is 2.5 K. The static stripe order in the large single crystals has been studied by neutron scattering method$^{[2]}$. [1] A. R. Moodenbaugh \textit{et al}, Phys. Rev. B, 38(1988)4596. [2] J. M. Tranquada \textit{et al}, Nature, 429(2004)534. [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