Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session B39: Heavy Fermion Superconductivity |
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Sponsoring Units: DCMP Chair: John Sarrao, Los Alamos National Lab Room: LACC 514 |
Monday, March 21, 2005 11:15AM - 11:27AM |
B39.00001: BCS superconductivity in mixed valence and heavy fermion superconductors Lev P. Gor'kov, Victor Barzykin We consider competition of Kondo effect and s-wave superconductivity in heavy fermion and mixed valence superconductors, using the slave boson $1/N$ approach for the periodic Anderson model. Similar to the well known results for single-impurity Kondo effect in superconductors, we have found that re-entrant behavior of the superconducting transition temperature, $T_c$, should be observed in heavy fermion superconductors as a function of model parameters or concentration of impurities. Suppression of $T_c$ in mixed valence superconductors is much weaker, without re-entrant behavior of $T_c$. Our results have most validity in the low-temperature regime. [Preview Abstract] |
Monday, March 21, 2005 11:27AM - 11:39AM |
B39.00002: Strong-Weak Coupling Self-Duality and Dimensional Reduction in the Two-Dimensional p+ip Superconducting Arrays and Frustrated Magnets Cenke Xu, Joel Moore We discuss models of superconducting arrays and frustrated magnets in two dimensions which show quantum phase transitions and self-dualities that are characteristic of one-dimensional problems. The first part of the talk explains how the geometric dependence of Josephson tunneling in time-reversal-breaking superconductors leads naturally to effective Hamiltonians containing four-point interactions rather than two-point interactions. This work was motivated by the observation of possible T-breaking p+ip order in Sr2RuO4, but similar four-point interactions appear in the 1/S expansion of certain standard models of frustrated magnetism. We show that many models on the square lattice with four-point interactions contain infinitely many gauge-like symmetries, and generalize the self-duality of the quantum Ising model in one dimension to related models in all higher dimensions. The existence of these nonperturbative self-dualities gives exact information on the phase diagram of the superconducting array models and on the phase transition between globally T-ordered and globally T-breaking states. [Preview Abstract] |
Monday, March 21, 2005 11:39AM - 11:51AM |
B39.00003: Two Superconducting Transitions in Heavy Fermion CePt3Si G.R. Stewart, J.S. Kim, P. Kumar, D.J. Mixson, D. Burnette Using small amounts of doping in CePt$_{3}$Si, along with annealing up to 1300 $^{\circ}$C, we have discovered two very distinct superconducting transitions in good analogy to U$_{1-x}$Th$_{x}$Be$_{13}$. We have characterized these samples with specific heat, $\chi $, and $\rho $ in zero and applied magnetic field and created a phase diagram to track the existence of the two transitions as a function of several materials parameters. The sum of the discontinuities, $\Delta $C, in the specific heat at T$_{c1}$ ($\approx $0.8 K) and T$_{c2}$ ($\approx $0.55 K) for both transitions exceeds the size of $\Delta $C for pure CePt$_{3}$Si by over a factor of four. The upper transition appears to be almost totally suppressed with impurites at the 100 ppm level, indicative of non-conventional superconductivity, while the lower transition is much more robust. [Preview Abstract] |
Monday, March 21, 2005 11:51AM - 12:03PM |
B39.00004: Fulde-Ferrell-Larkin-Ovchinnikov state in d-wave superconductivity K. Maki, H. Won, F. Weickert, P. Gegenwart Within the BCS theory of d-wave superconductivity we have analysed $H_{c2}(t, \phi)$ for ${\bf H}$ parallel to the a-b plane in a heavy fermion superconductor CeCoIn$_{5}$. We describe both the angle dependence and the temperature dependence, though the present theory predict the second order phase transition at $H=H_{c2}$. Also we obtain the local quasiparticle density of states $G({\bf r}, E)$ in the vicinity of $H=H_{c2} (t, \phi)$, which can be tested by STM and NMR for example. [Preview Abstract] |
Monday, March 21, 2005 12:03PM - 12:15PM |
B39.00005: Local Structure Around Sn in CeCoIn$_{5-x}$Sn$_x$ Million Daniel, Eric D. Bauer, Sang-Wook Han, Corwin H. Booth, Andrew L. Cornelius, John L. Sarrao CeCoIn$_5$ is an ambient pressure superconductor with a transition temperature of 2.3 K. Recent experiments have shown that superconductivity is easily destroyed with the replacement of In with Sn. The role of Sn on the superconducting state in the CeCoIn$_{5-x}$Sn$_x$ alloy has been investigated by the extended x-ray absorption fine structure (EXAFS) technique. Our fit results for $x$ = 0.09, 0.12, 0.18, and 0.24 show a major fraction of the dopant Sn atoms preferentially residing on the planar In(1) site. This result is consistent with the two-dimensional superconducting state in CeCoIn$_5$ and will be discussed in relation to the observed rapid suppression of superconductivity in the CeCoIn$_{5-x}$Sn$_x$ system. [Preview Abstract] |
Monday, March 21, 2005 12:15PM - 12:27PM |
B39.00006: Angle Resolved Photoemission study of CeMIn$_5$ (M = Co, Rh)$^*$ F. Wang, J.W. Allen, J.D. Denlinger, Kai Rossnagel, M.B. Maple, S. Elgazaar, P.M. Oppeneer Angle-resolved photoemission (ARPES) and Fermi Surface (FS) mapping measurements are presented for the paramagnetic phases of the heavy fermion superconductor CeCoIn$_5$, the antiferromagnet CeRhIn$_5 $, and the quantum critical crossover alloy Ce(Co$_{0.8}$Rh$_{0.2}$)In$_5$, revealing more detailed electronic structure information than previously reported. Analysis of multi-Brillouin zone ARPES electronic structure maps allows detailed comparison of the FS topologies and band dispersions between compounds with different compositions and also with the FS structures observed in de Haas van Alphen experiments. Multiple sheets of large-orbit quasi-2D pieces of FS are observed to be in agreement with LDA predictions, but small-size contours near the zone center are more discrepant. The data will be assessed in relation to current thinking about the physics of these interesting materials. \vspace{0.1cm} \\ $^*$ Supported by the U.S. NSF at U. Mich. (DMR-03-02825) and by the DOE at the Advanced Light Source (DE-AC03-76SF00098). [Preview Abstract] |
Monday, March 21, 2005 12:27PM - 12:39PM |
B39.00007: Scaling Behavior of Angular Magnetoresistivity of CeCoIn5 Single Crystals T. Hu, H. Xiao, C.C. Almasan, T.A. Sayles, M.B. Maple The angular dependence of in-plane magnetoresistivity of single crystals of CeCoIn$_{5}$ was measured above the zero-field critical temperature T$_{c 0}$ over a temperature T range from T$_{c0}$ to 10 K and applied magnetic fields H up to 14 T. We constructed an H - T phase diagram above T$_{c0}$ for this compound and identified a boundary, which separates regions of positive and negative magnetoresistance in the non-Fermi liquid regime. A critical angle $\theta _{c}$ ($\theta $ is the angle between the direction of the magnetic field and the c axis of the single crystal) is found in the positive magnetoresistance region, which may be correlated with the anisotropy of this material. The in-plane angular magnetoresistivity scales both above and below $\theta _{c}$ with different scaling functions. The temperature and magnetic field dependence of the critical angle $\theta _{c}$ will also be discussed. Our results show that one of the scalings could be the result of flux flow dissipation. [Preview Abstract] |
Monday, March 21, 2005 12:39PM - 12:51PM |
B39.00008: Field dependence of low-temperature resistivity in CeIrIn5 Hamideh Shakeripour, Shiyan Li, Louis Taillefer, C Petrovic, Johnpierre Paglione We report on a study of the in-plane and inter-plane resistivity of the heavy-fermion superconductor CeIrIn$_{5}$. Measurements were performed down to 40 mK in a magnetic field applied parallel to the c axis. We analyze how the temperature dependence of the resistivity evolves with magnetic field, both inside and outside the Fermi-liquid regime, and compare this evolution with that of CeCoIn$_{5}$, a closely related material with a field-induced quantum critical point. [Preview Abstract] |
Monday, March 21, 2005 12:51PM - 1:03PM |
B39.00009: Point Contact Spectroscopy Study of CeCoIn$_5$: Evidence for Unconventional Pairing in a Multi-Band Heavy Fermion Superconductor P. M. C. Rourke, C. S. Turel, M. A. Tanatar, C. Petrovic, J. Y. T. Wei Point-contact spectroscopy was performed on single crystals of the heavy-fermion superconductor CeCoIn$_5$ in the temperature range 150mK to 2.5K. A pulsed measurement technique ensured minimal Joule heating over a wide voltage range. The spectra show Andreev-reflection characteristics with multiple structures which depend on junction impedance. Spectral analysis using the generalized BTK formalism revealed two nodal order-parameter components, with amplitudes $\Delta_1$=0.95 $\pm$0.15meV and $\Delta_2$=2.4$\pm$0.3meV which evolve differently with temperature. These observations indicate a highly unconventional pairing mechanism, possibly involving multiple bands [1]. Measurements are also done in a magnetic field to study the field-evolution of the order-parameter components we observed. \\ ~[1]~P.M.C. Rourke, \emph{et al}. cond-mat/0409562. \\ Work supported by: NSERC, CFI/OIT, MMO/EMK and the Canadian Institute for Advanced Research. Work at Brookhaven supported by: Division of Materials Sciences, Office of Basic Energy Sciences, US Department of Energy under contract no. DE-AC02- 98CH10886. [Preview Abstract] |
Monday, March 21, 2005 1:03PM - 1:15PM |
B39.00010: Angular Dependent Magnetoresistivity Studies of CeCoIn5 Single Crystals H. Xiao, T. Hu, T. Katuwal, P. Gyawali, C.C. Almasan, T.A. Sayles, M.B. Maple In-plane angular magnetoresistivity measurements were made on CeCoIn$_{5}$ single crystals at low applied magnetic fields H (H $\le $ 2.5 T) around the zero field critical temperature T$_{c0}$. The angular conductivity measured at different temperatures and applied fields can be well fitted with a recently suggested flux flow model, in which the in-plane conductivity is the sum of quasiparticle and flux-flow contributions. This indicates the presence of flux flow dissipation in the measured temperature and magnetic field range. The temperature and magnetic field dependence of the three fitting coefficients will also be discussed. Moreover, angular magnetoresistivity curves scale below a certain critical angle $\theta _{c}$ ($\theta $ is the angle between the direction of H and c axis of the crystal). This result has previously been obtained in the mixed state of cuprates. Therefore, the scaling appears to be a result of flux flow dissipation in this heavy fermion compound.. [Preview Abstract] |
Monday, March 21, 2005 1:15PM - 1:27PM |
B39.00011: Pressure Dependence of the Field-tuned Quantum Critical Point in CeCoIn5 Filip Ronning, Cigdem Capan, Roman Movshovich, Joe D. Thompson, Eric D. Bauer, John L. Sarrao Non-Fermi liquid behavior, as characterized by a T-linear resistivity and a T log(T) behavior in specific heat, is observed in zero field in the heavy fermion system CeCoIn$_{5}$. The application of magnetic field has revealed a field tuned quantum critical point surprisingly coincident with the superconducting H$_{c2}$. Neither field orientation nor Sn doping has been able to separate H$_{c2}$ from the quantum critical field implying that the two are more than accidentally linked together. We further investigate the nature of the quantum critical point with resistivity measurements under pressure and magnetic field simultaneously. [Preview Abstract] |
Monday, March 21, 2005 1:27PM - 1:39PM |
B39.00012: Giant Nernst effect in d-wave density waves Kazumi Maki, Balazs Dora, Attila Virosztek, Andras Vanyolos Recently we have shown that the d-wave density wave exhibits a large negative Nernst effect in the presence of a magnetic field perpendicular to the conducting plane. Such Nernst effects have been seen in pseudogap phase in high Tc cuprate superconductors LSCO,YBCO,Bi2212 [1] and more recently in the pseudogap phase in heavy fermion superconductor CeCoIn$_5$ [2]. In particular we can describe the field dependence of the Nernst coefficient of CeCoIn$_5$ very consistently in terms of d-wave density wave. We shall report our analysis of other properties of the pseudogap phase in high $T_c$ cuprates in terms of d-DW. [1] Y. Wan et al, Phys. Rev. Lett. 88,257003(2002) [2] R. Bel et al, Phys. Rev. Lett. 92,217002(2004) [Preview Abstract] |
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