Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session H13: Superconducting Magneto-Transport Properties |
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Sponsoring Units: DCMP Chair: Carmen Alamasan, Kent State University Room: LACC 402B |
Tuesday, March 22, 2005 8:00AM - 8:12AM |
H13.00001: Superconductivity and possible charge Kondo effect in Tl-doped PbTe Y. Matsushita, H. Bluhm, T. H. Geballe, I. R. Fisher We report results of low-temperature thermodynamic and transport measurements of Pb$_{1-x}$Tl$_x$Te single crystals for Tl concentrations up to the solubility limit of approximately 1.5$\%$. For $x$ greater than approximately 0.3$\%$, the samples superconduct with a maximum $T_c$ of approximately 1.4 K for the highest Tl concentrations. For all doped samples, we observe an anomalous low-temperature upturn in the resistivity that saturates below 1 K and that scales in magnitude with the Tl concentration. The temperature and field dependence of this upturn are consistent with Kondo-like behavior of a nonmagnetic degenerate two-level system. [Preview Abstract] |
Tuesday, March 22, 2005 8:12AM - 8:24AM |
H13.00002: Quantum Fluctuations and High-Field Phase Diagram of the Infinite Layer Superconductor Sr$_{0.9}$M$_{0.1}$CuO$_2$ (M = La, Gd) C.R. Hughes, A.D. Beyer, N-C. Yeh, V.S. Zapf, M-S. Park, K-H. Kim, S-I. Lee Competing orders in cuprate superconductors can affect the cuprate's low energy excitations, and thus result in unconventional quantum fluctuations that also alter vortex dynamics. We have examined this behavior in the simplest form of cuprates, the electron doped infinite layer Sr$_{0.9}$M$_{0.1}$CuO$_{2}$ (T$_{c} \quad \approx $ 43 K). Using high magnetic field (H$\le $60 T) penetration depth and magnetization vs. H measurements, and lower field (H$\le $8 T) 3$^{rd}$ harmonic susceptibility and DC transport measurements, the low-temperature high-field behavior of Sr$_{0.9}$La$_{0.1}$CuO$_{2}$ is studied from 1.9 to 45 K. The\textbf{ }upper critical (H$_{c2})$ and irreversibility (H$_{irr})$ fields associated with the ab plane and c-axis are determined, and the small ratio H$_{irr}^{ab}$/H$_{c2}^{ab}$ = 0.27 (extrapolated to 0 K) indicates large quantum fluctuations and thus proximity to a quantum critical point. The insensitivity of the superconductivity to off planar Gd and the ab plane vs. c-axis magnetic anisotropy are also examined with respect to competing orders and quantum criticality. [Preview Abstract] |
Tuesday, March 22, 2005 8:24AM - 8:36AM |
H13.00003: Upper Critical Field in C-Doped MgB2 Thin Films and Coated Fibers V. Ferrando, J. Chen, P. Orgiani, A.V. Pogrebnyakov, X.X. Xi, Qi Li, J. Redwing We have studied H$_{c2}$ and its anisotropy $\gamma $ of C-doped MgB$_{2}$ thin films grown on (0001) SiC single crystal substrates and SiC/W fibers by hybrid physical-chemical vapor deposition (HPCVD). Residual resistivity increases systematically with doping, but Tc is not affected seriously. The H$_{c2}$ in both direction was found to increase with increasing residual resistivity. In the field range between 1 - 9 T, the slope of Hc$_{2}^{\bot ab}$ (T) increases from about 0.1Tesla/K to1.1Tesla/K and the slope of Hc$_{2}^{//ab}$ (T) increases from about 0.6 T/K to 2.2 T/K. The temperature dependence of the anisotropy changes dramatically with the doping level. In the fiber samples, large upper critical field similar to Hc$_{2}^{//ab}$ (T) in thin films was obtained. The results measured in pulsed higher magnetic fields (60T) will also be presented. The effects will be compared with the recent theoretical predictions on two band superconductors. [Preview Abstract] |
Tuesday, March 22, 2005 8:36AM - 8:48AM |
H13.00004: HiTc Resistivity Measurements and QCP in CLBLCO Superconductors Yakov Eckstein, Byron Watkins, KHanan Chashka, Arkady Knizhnik Measurements of resistivity in ceramic (Ca$_{x}$La$_{1-x})$(Ba$_{c-x}$La$_{2-c+x})$Cu$_{3}$O$_{y}$ for (1) c=1.75 and (2) c=1.5 were taken as function of oxygen y. By using oxygen doping for the case (1) and x=0.1, one can dope this compound from non SC (superconductivity) underdoped to non SC overdoped. In the underdoped region there exists a temperature such that below this T, dR/dT is negative before superconductivity sets in. We also find dR/dT becomes negative at low T for the non superconducting samples in the extreme overdoped regime. No quantum critical point (QCP) is observed for doping less than y=7.334, which constitutes the entire SC range. The compound with c=1.5 and x=0 is never superconducting. All these samples exhibit negative slope in their R-T characterizations. The temperature at which dR/dT becomes negative is lower when doping in higher. [Preview Abstract] |
Tuesday, March 22, 2005 8:48AM - 9:00AM |
H13.00005: Hall Effect in CLBLCO Superconductors Byron Watkins, KHanan Chashka, Arkady Knizhnik, Yakov Eckstein Electrical charge transport carrier concentration trends were observed with Hall effect experiments in (Ca$_{x}$La$_{1-x})$(Ba$_{1.75-x}$La$_{0.25+x})$Cu$_{3}$O$_{y}$. All values of x yield similar trends in R$_{H}$ vs. T, but increasing doping (y) reduces R$_{H}$ as expected. All samples that exhibit superconductivity (SC) also exhibit a maximum Hall coefficient at approximately 2T$_{C}$. Contrarily, in the extreme doping cases (non SC samples) no maxima are observed and the underdoped cases exhibit insulator-like increased R$_{H}$ at lower T. A full description of experiment and analysis will be presented. [Preview Abstract] |
Tuesday, March 22, 2005 9:00AM - 9:12AM |
H13.00006: Low temperature anisotropic magnetoresistance studies of the electron-doped superconductor Pr$_{1.85}$Ce$_{0.15}$CuO$_4$ Weiqiang Yu, P. Li, J. Higgins, Y. Dagan, B. Liang, R.L. Greene We report the low temperature dc transport properties of crystals of electron-doped superconductor Pr$_{1.85}$Ce$_{0.15} $CuO$_4$(Tc~25K). By applying the magnetic field beyond H$_{C2} $, both in-plane and out-of-plane (c-axis) resistivity have a similar metallic temperature dependence with an upturn as the temperature drops below T=13K. For T<32K, a negative magnetoresistance develops in the c-axis resistivity at low magnetic field, followed by a positive magnetoresistance at high field. In contrast, the in-plane transport only shows a monotonic positive magnetoresistance in the same (H, T) region. The possible origin of these behaviors and a comparison with hole-doped superconductors will be given. (Supported by NSF DMR- 0352735) [Preview Abstract] |
Tuesday, March 22, 2005 9:12AM - 9:24AM |
H13.00007: Superconducting Critical Field Curves in Uranium-Niobium alloys Jason C. Cooley, W. Larry Hults, Jason C. Lashley, James L. Smith, George M. Schmiedeshoff The uranium niobium binary alloy system exhibits a rich collection of phenomena for study. The composition range from 0 wt.{\%} Nb to 10 wt.{\%} Nb exhibits multiple crystallographic phases with interesting properties such as superconductivity, charge density waves and shape memory effects. We have extended the range of our resistivity measurements to as low as 400mK in order to map the critical field curves of these superconducting alloys. As a function of temperature some of the critical field curves have positive curvature which is somewhat correlated with the normal state temperature dependence of the resistivity. Work supported by the United States Department of Energy and the National Science Foundation. [Preview Abstract] |
Tuesday, March 22, 2005 9:24AM - 9:36AM |
H13.00008: New Transition in the Vortex Liquid State: intrinsic limit of the irreversibility line Wai-Kwong Kwok, Goran Karapetrov, Ulrich Welp, Andreas Rydh, George Crabtree, Lisa Paulius, Jordi Figueras, Teresa Puig, Xavier Obradors We have carried out angular dependent magneto-transport measurements on optimally doped, untwinned YBCO crystals irradiated with high energy heavy ions to determine the onset of vortex line tension in the vortex liquid state. The matching field was controlled and kept at a low level to partially preserve the first order vortex lattice melting transition. A Bose glass transition is observed below the lower critical point which then transforms into a first order phase transition near 5 Tesla. The locus of points which indicate the onset of vortex line tension overlaps with the Bose glass transition line at low fields and then deviates at higher fields, indicating a new transition line in the vortex liquid state. This new line in the vortex liquid phase extends beyond the upper critical point.$\backslash $This work was supported by the U.S. Department of Energy, BES, Materials Science under Contract No. W-31-109-ENG-38 at Argonne National Laboratory. [Preview Abstract] |
Tuesday, March 22, 2005 9:36AM - 9:48AM |
H13.00009: Evolution of the Hall effect in CeCoIn$_5$; non-Fermi to Fermi liquid crossover Yasuyuki Nakajima, Koichi Izawa, Yuji Matsuda, Hiroaki Shishido, Rikio Settai, Yoshichika Onuki, Hiroshi Kontani, Masato Hedo, Yoshiya Uwatoko, Takehiko Matsumoto Heavy fermion superconductor CeCoIn$_5$ ($T_{\rm c}$=2.3K) is located in the vicinity of the antiferromagnetic quantum critical point (QCP). At ambient pressure, the transport properties show non-Fermi liquid behavior, for example, the resistivity $\rho \propto T$. With applying pressure, non-Fermi liquid behavior is suppressed and Fermi liquid behavior recovers. To investigate the electronic transport properties in non-Fermi and Fermi liquid regions, we measured the pressure dependence of the normal-state Hall effect of CeCoIn$_5$ up to 2.51 GPa. At ambient pressure, the Hall coefficient varies as $R_{\rm H} \propto T^{-1}$. With increasing pressure, $R_{\rm H}$ approaches $T$-independent value which is expected for conventional Fermi liquid metals. These results indicate that $T^{-1}$- dependence of $R_{\rm H}$ is a new hallmark of electronic transport properties in the presence of strong antiferromagnetic spin fluctuation near a QCP. [Preview Abstract] |
Tuesday, March 22, 2005 9:48AM - 10:00AM |
H13.00010: Magnetisation and the Irreversibility Line in Strongly Underdoped YBa$_2$Cu$_3$O$_{7-\delta}$ Alix McCollam, Stephen Julian, Ruixing Liang, Douglas Bonn, Walter Hardy Torque magnetometry experiments were made on a high purity single crystal of YBa$_2$Cu$_3$O$_{6.354}$. The irreversibility line $H_{irr}(T)$ was measured and found to lie very low in field, with a high temperature end-point at 5~K, far below the superconducting $T_c$ of 12~K, and a steep upturn at the lowest temperatures. Considerable suppression of $H_{irr}(T)$ in the presence of a small AC magnetic field indicates that the irreversibilty line is distinct from a flux-lattice melting transition in this material. A second feature $H^*(T)$, observed in the magnetisation data at fields above $H_{irr}(T)$, was unaffected by a similar AC field. Torque measurements as a function of crystal orientation revealed a sharp lock-in transition at angles of field close to the $ab$-plane, and illustrate the high degree of anisotropy in this system at very low doping levels. [Preview Abstract] |
Tuesday, March 22, 2005 10:00AM - 10:12AM |
H13.00011: Destruction of superconductivity and pseudogap closing in Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+\delta}$ by 58 T magnetic field S. Ono, Yoichi Ando, F.F. Balakirev, J.B. Betts, G.S. Boebinger We measure the magnetic-field dependence of the c-axis resistivity $\rho_c(H)$ in a series of Bi$_2$Sr$_{2-x} $La$_x$CuO$_{6+\delta}$ (BSLCO) single crystals for a wide doping range using pulsed magnetic fields up to 58 T. [1] The behavior of $\rho_c(H)$ is examined with the recent determination of the upper critical field $H_{c2}$ by the Nernst effect measurements for the same BSLCO crystals. We find that the peak in $\rho_c(H)$ shows up at a field $H_p$ that is much lower than $H_{c2}$ and there is no discernable feature in $\rho_c(H)$ at $H_{c2}$. It is found that the doping dependence of $H_p$ essentially track that of $T_c$. Moreover, a new method is proposed for estimating the pseudogap closing field $H_{pg}$ from our BSLCO data, because we found that the method to estimate $H_{pg}$ in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ [2] does not apply to our data. [1] S. Ono et al., cond-mat/0408603, To appear in PRB [2] T. Shibauchi et al. Phys. Rev. Lett. {\bf 86}, 5763 (2001). [Preview Abstract] |
Tuesday, March 22, 2005 10:12AM - 10:24AM |
H13.00012: Electrical Transport Study of Fluctuations for the Superconducting Transition in the Electron Doped Cuprate $Pr_{2-x}Ce_{x}CuO_{4}$ Jacques Renaud, Patrick Fournier, Jacques Beauvais, Claude Bourbonnais, Mike Denhoff It is well known that due to their very short coherence length and high anisotropy, high-Tc superconductors have a region of fluctuations around Tc that is experimentally accessible. Electrical transport in the fluctuation region can be related to dimensionality and the two critical exponents, $\nu$ for the correlation length and $\textit{z}$ for the dynamics of the fluctuations. In this talk we report on the temperature dependence of the paraconductivity and the current-voltage measurement for thin films of the electron doped superconductor $Pr_{2-x}Ce_{x}CuO_{4}$. We use the Fisher, Fisher and Huse[1] dynamical scaling approach and the Lawrence-Doniach model to obtain a coherent picture of the superconducting phase transition in this material. The effect of disorder on our analysis will be addressed. [1] D. S. Fisher, M. P. A. Fisher and D. A. Huse, \textsl{Phys. Rev. B} \textbf{43}, 130 (1991). [Preview Abstract] |
Tuesday, March 22, 2005 10:24AM - 10:36AM |
H13.00013: Angular Magnetoresistivity Measurements in the Pseudogap Region of $Y_{1-x}Pr_{x}Ba_{2}Cu_{3}O_{7-\delta}$ T. Katuwal, P. Gyawali, C.C. Almasan, B.J. Taylor, M.B. Maple We carried out a detail investigation of the angular dependence of in-plane conductivity $\sigma_{ab}(\theta)$ ($\theta$ is the angle between the direction of H and c-axis of the sample) near and above the zero field critical temperature $T_{c0}$ of $Y_{1-x}Pr_{x}Ba_{2}Cu_{3}O_{7-\delta}$ single crystals for applied magnetic field H up to 14 T. We studied a large range of Pr concentrations x; i. e. $0.20 \leq x \leq 0.53$. We write the total in-plane conductivity as the sum of quasiparticle and flux-flow type contributions. This expression fits very well the data in the pseudogap region up to a temperature $T_{\phi}$ ($T_{c0} < T_{\phi} < T^{*}$, where $T^{*}$ is the pseudogap temperature) and for all values of H. Above $T_{\phi}$, the quasiparticle component alone is able to fit the data perfectly. These results clearly indicate the presence of vortex like contribution to dissipation above $T_{c0}$. The temperature and magnetic field dependence of the three fitting coefficients will also be discussed. A plot of the $T_{\phi}$ $vs$ $x$ phase diagram is compared with the corresponding $T_{c0}(x)$ in order to show the extent of $T_{\phi}$ above $T_{c0}$. The ratio of $T_{\phi}/T_{c0}$ increases with increasing x doping. [Preview Abstract] |
Tuesday, March 22, 2005 10:36AM - 10:48AM |
H13.00014: Remarkable doping dependence of the spin magnetoresistance in Pr$_{2-x}$Ce$_x$CuO$_4$ Yoram Dagan, M.C. Barr, W.M. Fisher, R.L. Greene, T. Dhakal, A. Biswas The temperature, doping and field dependences of the magnetoresistance (MR) in Pr$_{2-x}$Ce$_{x}$CuO$_{4-\delta }$ films are reported. We distinguish between orbital MR, found when the magnetic field is applied perpendicular to the ab planes, and the nearly isotropic spin MR. The latter is the major MR effect in the superconducting samples. At low temperatures, the isotropic spin MR appears in the underdoped region, increases in magnitude at optimum doping and suddenly vanishes at x=0.16. This remarkable disappearance of the spin MR can be related to the Quantum critical point we have previously reported. [1] We also find a correlation between the spin MR and the upturn in resistivity (d$\rho $/dT$<$0), which suggests that the upturn originates from spin scattering processes. (See also cond-mat/ 0408490) [1] Y. Dagan \textit{et al.} Phys. Rev. Lett.\textbf{92}, 167001 (2004). [Preview Abstract] |
Tuesday, March 22, 2005 10:48AM - 11:00AM |
H13.00015: The high-field transport property of Sm-Ba-Cu-O bulk materials with different nano-scale additions Y.C. Liao, S.Y. Chen, I.G. Chen, M.K. Wu The nano-scale additions, such as, RE$_{2}$BaCuO$_{5}$ (RE= Y, Sm, and Nd) particles, in the melt-textured-growth Sm-Ba-Cu-O bulk material can enhance the critical current density (J$_{C})$,especially in high magnetic field. These particles contribute to the nano-scale composition fluctuation and thus the variation of T$_{C}$ in a nano-scale. The $\delta $T$_{C}$ pinning is the reason of high-field peak effect in J$_{C}$(H). We found that there are two characteristic temperatures shown in the high-field ( 2$\sim $ 7 tesla) R(T) curves in the sample with the peak effect. This is in contrast to the sample without the nano-scale additions, which exhibits only one transition temperature. It suggests that there are two different regimes with varying superconducting transitions in the former sample. The detailed mechanism of this behavior will be discussed. [Preview Abstract] |
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