Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session L10: Heavy Fermions in the 115 Compounds |
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Sponsoring Units: DCMP Chair: Jerome Rech, Argonne National Laboratory Room: Colorado Convention Center Korbel 1E |
Tuesday, March 6, 2007 2:30PM - 2:42PM |
L10.00001: Incoherent Non-Fermi Liquid Scattering in a Kondo Lattice Johnpierre Paglione, T.A. Sayles, P. -C. Ho, M.B. Maple The effect of Kondo lattice dilution was investigated in the heavy-fermion superconductor CeCoIn$_5$ to study the evolution of unconventional superconductivity and non-Fermi liquid properties. A systematic substitution of both non-magnetic (full or empty $f$-shell) and large, stable $f$-moment rare earth impurities into high-quality single-crystal specimens of Ce$_{1-x}$R$_x$CoIn$_5$ (where R=Y, Pr, Gd, Er and Lu) has revealed two contrasting features. First, both superconducting electron pair-breaking and the suppression of Kondo coherence proceed in a manner which is insensitive to the magnetic state of the dopant atom, suggesting spin-independent disorder is the dominant perturbation in both phenomena. In contrast, the evolution of the non-Fermi liquid properties with substitution shows a striking sensitivity to the dopant atom's f-moment configuration. [Preview Abstract] |
Tuesday, March 6, 2007 2:42PM - 2:54PM |
L10.00002: Effects of self-irradiation on local crystal structure and 5$f$ localization in PuCoGa$_5$ C. H. Booth, M. Daniel, R. E. Wilson, E. D. Bauer, J. N. Mitchell, N. O. Moreno, L. A. Morales, J. L. Sarrao, P. G. Allen X-ray absorption fine-structure (XAFS) measurements demonstrate the structural and electronic changes involved in destroying superconductivity in PuCoGa$_5$ due to self-irradiation damage. In particular, the Pu $L_\textrm{III}$-edge data indicate a more localized $f$-orbital relative to the itinerant paramagnet UCoGa$_5$, potentially increasing with radiation damage. Moreover, the local crystal structure in aged material is disordered much more strongly than expected, consistent with all atoms within a damage cascade displaced from their equilibrium positions. [Preview Abstract] |
Tuesday, March 6, 2007 2:54PM - 3:06PM |
L10.00003: Superconductivity due to cooperative two-channel Kondo effect Maxim Dzero, Kasturi Basu, Piers Coleman We discuss the application of the co-operative two-channel Kondo model to describe the low temperature properties of the Ce and Pu- based 115's. Based on the crystal field multiplet structure for Ce and Pu ions in tetragonal symmetry, we employ the group theory to justify the validity of the two-channel Kondo physics. Additional screening channel contributes to destabilization of the Fermi liquid and leads to development of the heavy Fermi surface. The fluctuations between the zero modes for the Kondo singlets leads to divergent composite pair susceptibility. [Preview Abstract] |
Tuesday, March 6, 2007 3:06PM - 3:18PM |
L10.00004: Coexistence of antiferromagnetism and superconductivity in a model for CeRhIn$_5$ Jose V. Alvarez, Felix Yndurain The finite temperature phase diagram of CeRhIn$_5$ as a function of presure and magnetic field has three main highlights: 1) the competitive coexistence of metallic antiferromagnetism and superconductivity, 2) the abrupt dissapearance of antiferromagnetism when the Neel and superconducting temperatures become equal at a critical pressure P$_c$ and 3) the reentrance of the antiferromagnetic phase in a range of pressures larger than P$_c$ when a magnetic field is applied. Based on first-principles band structure calculations, we propose a quasi-two-dimensional model of interacting electrons, which reproduces, at the mean-field level, the central features of the phase diagram. We also discuss the divergence of the cyclotron mass observed in dHvA oscilations and the amount entropy released at the ordering temperatures. [Preview Abstract] |
Tuesday, March 6, 2007 3:18PM - 3:30PM |
L10.00005: Quantum Criticality in Cd doped CeMIn$_{5}$. Filip Ronning, Yoshi Tokiwa, Joe Thompson, Roman Movshovich, Long Pham, Zachary Fisk In pure CeCoIn$_{5}$ the application of magnetic field has revealed a field tuned quantum critical point surprisingly coincident with the superconducting H$_{c2}$. The application of pressure suppressed the antiferromagnetic fluctuations in the system and pushed the quantum critical field inside the superconducting dome. By substituting Cd for In it was shown that one can quickly induce the antiferromagnetic state. With predominantly thermodynamic probes, such as specific heat, we investigate how the appearance of long range antiferromagnetic order induced by Cd doping influences the field tuned quantum critical behavior. This will also be contrasted with the behavior found for the antiferromagnetic quantum critical point seen in CeRhIn$_{5}$ under pressure. [Preview Abstract] |
Tuesday, March 6, 2007 3:30PM - 3:42PM |
L10.00006: Multiple vortex phases in the heavy fermion superconductor CeCoIn$_{5}$ A. D. Bianchi, Z. Fisk, M. Kenzelmann, J. Mesot, J. Kohlbrecher, M. Zolliker, L. DeBeer-Schmitt, M. R. Eskildsen, J. S. White, E. M. Forgan, R. Movshovich, E. D. Bauer, J. L. Sarrao, C. Petrovic We report the entire HT-phase diagram of the vortex lattice (VL) in CeCoIn$_{5}$ for fields applied along the crystallographic $c$-axis. At the upper critical field $H_{c2}$ of about 5~T and 50~mK, we observe a distorted hexagonal flux lattice, which first gives way to a rhombic lattice at 4.3~T and then to a square lattice at 3.3~T, before entering the previously reported flux lattices at lower fields. The distorted hexagonal phase extends to lower fields and higher temperatures than the $H$-$T$-phase space that was previously assigned to a inhomogeneous FFLO state by magnetization and NMR measurements. Surprisingly, we also observed an increase of the flux lattice form factor as a function of increasing field in the rhombic phase, in constrast to the flux lattice in most superconductors. We will discuss the relevance of these results for the presence of the FFLO and magnetic phases. [Preview Abstract] |
Tuesday, March 6, 2007 3:42PM - 3:54PM |
L10.00007: Nature of a possible FFLO state in CeCoIn$_5$ as revealed by NMR. Georgios Koutroulakis, Vesna Mitrovic, Marc-Andre Vachon, Mladen Horvatic, Claude Berthier, Georg Knebel, Gerard Lapertot, Jacques Flouquet We report low temperature $^{115}$In nuclear magnetic resonance (NMR) measurements of the heavy-fermion superconductor CeCoIn$_5$ in high magnetic fields. We will discuss the implications of our findings for the nature of a possible inhomogeneous superconducting state, the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, in this compound. [Preview Abstract] |
Tuesday, March 6, 2007 3:54PM - 4:06PM |
L10.00008: Superconductivity and magnetism in heavy-fermion systems Daniel E. Sheehy, Joerg Schmalian Recent experiments on CeCoIn$_5$ have observed coexisting superconductivity and magnetic order under an applied magnetic field near the Pauli limit. Motivated by such observations, we study the interplay between pairing and magnetism in the SU(N) Kondo lattice model, believed to provide an accurate description at low temperatures of such heavy-fermion systems. We present results for the phase diagram as a function of temperature and magnetic field. [Preview Abstract] |
Tuesday, March 6, 2007 4:06PM - 4:18PM |
L10.00009: Effect of pressure on hole-doped CeCoIn$_{5}$ and CeRhIn$_{5}$. V. A. Sidorov, Tuson Park, J. D. Thompson, L. D. Pham, S. Maquilon, Z. Fisk With one less p-electron than In, Cd or Hg adds one hole per substituted In in CeMIn$_{5}$ (M=Co,Rh, Ir). Progressive Cd/Hg substitutions tune the ground state of superconducting CeCoIn$_{5}$ to one of coexisting magnetism and superconductivity and eventually to antiferromagnetic only. This systematic evolution of states in doped CeCoIn$_{5}$ is reversed accurately by applied pressure and maps onto the temperature-pressure phase diagram of pure CeRhIn$_{5}$. These observations, together with the response of Cd-substituted CeRhIn$_{5}$ to applied pressure, show that ground states of CeMIn$_{5}$ are controlled by fine details of electronic structure and that disorder on the In site and different ionic radii of Cd and Hg have an insignificant effect. [Preview Abstract] |
Tuesday, March 6, 2007 4:18PM - 4:30PM |
L10.00010: Magnetic and electrical transport properties of Ce$_{1-x}$Nd$_{x}$CoIn$_{5}$ Cedomir Petrovic, Jacob Hudis, Rongwei Hu, Yongjae Lee, Vesna Mitrovic, Collin Broholm Single crystals of Ce$_{1-x}$Nd$_{x}$CoIn$_{5}$ (0$\le $x$\le $1) were grown by molten metallic flux technique. Synchrotron powder X-ray diffraction confirms phase purity and smooth evolution of the lattice parameters with increased Nd concentration. Evolution of the ground state in this alloy series between heavy fermion superconducting for x = 0 (CeCoIn$_{5})$ and antiferromagnetic for x = 1 (NdCoIn$_{5})$ will be presented. [Preview Abstract] |
Tuesday, March 6, 2007 4:30PM - 4:42PM |
L10.00011: In-plane torque measurements on CeCoIn$_5$ single crystals H. Xiao, T. Hu, C.C. Almasan, T.A. Sayles, M.B. Maple In-plane torque measurements were performed on single crystals of CeCoIn$_5$ in the mixed state in order to determine the symmetry of the superconducting gap. The reversible part of the mixed state torque shows a four fold symmetry. The sign of the four fold symmetry is positive. The amplitude of the in-plane torque first increases with increasing magnetic field H, and then decreases with further increasing field until it vanishes towards H$_{c2}$. Sharp irreversible peaks are present in the irreversible torque at 45, 135, 225, and 315$^{0}$. These experimental results imply d$_{xy}$ symmetry of the superconducting order parameter. We also performed in-plane torque measurements in the normal state. Another four fold symmetry is found which has a different origin than the one in the mixed state. The amplitude of the normal state torque has an $H^{4}$ dependence and it shows no saturation up to 14 T. This later four fold symmetry could be related with the symmetry of the Fermi surface. [Preview Abstract] |
Tuesday, March 6, 2007 4:42PM - 4:54PM |
L10.00012: Flux Growth of Heavy Fermion LiV$_2$O$_4$ Single Crystals S. Das, X. Zong, A. Niazi, D.C. Johnston The spinel-structure compound ${\rm LiV_2O_4}$ is a rare $d$- electron heavy fermion. Measurements on single crystals are needed to clarify the mechanism for the heavy fermion behavior. In addition, it is known that small concentrations ($< 1$ mol\%) of magnetic defects in the structure strongly affect the properties, and measurements on single crystals containing magnetic defects would help to understand the latter behaviors. Herein, we report growth at 950--1030~$^\circ$C of 1~mm$^3$ size octahedron-shaped ${\rm LiV_2O_4}$ single crystals using a self- flux technique. The magnetic susceptibility of the as-grown crystals shows a Curie-like upturn at low temperatures arising from $\approx 0.5$ mol\% magnetic defects within the spinel structure. After annealing at 700~$^\circ$C, the Curie-like upturn (and magnetic defects) disappeared in some crystals, thus revealing the known intrinsic nearly temperature-independent behavior below $\sim 20$~K\@. Preliminary heat capacity measurements on as-grown crystals containing magnetic defects showed a high linear specific heat coefficient $\gamma$ = 450 mJ/ (mole K${^2}$) at 1.8~K\@. Additional electronic tranport, magnetic and thermal measurements on both as-grown and annealed crystals will be presented. [Preview Abstract] |
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