Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session J46: Ce- and Yb-based Heavy-Fermion and Non-Fermi Liquid Systems |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Shanta Saha, University of Mayland Room: Mile High Ballroom 4E |
Tuesday, March 4, 2014 2:30PM - 2:42PM |
J46.00001: Reentrant quantum oscillations in CeIn$_3$ William A. Coniglio, David E. Graf, Ryan L. Stillwell, Ju-Hyun Park, Pedro Schlottmann, Eric C. Palm, Tim P. Murphy, Jason C. Cooley, Stanley W. Tozer Heavy fermion conductor CeIn$_3$ is a low temperature antiferromagnet with a N\'eel transition at 10\,K, 2.6\,GPa, and 62\,T. We show that N\'eel and Lifshitz transitions both introduce Fermi surface reconstruction, and the difference in temperature dependence between them leads to surprising reentrant behavior of certain Shubnikov de Haas orbits as a function of field, temperature, and pressure. We use a diamond anvil cell in a helium-3 fridge in pulsed magnetic fields to cover almost the entire phase space of the antiferromagnetic state. Our high resolution resistivity probe is a Tunnel Diode Oscillator that is mounted adjacent to the pressure cell within the bore of the magnet. We confirm the extraordinary sensitivity of the technique by observing the 69 kT Shubnikov de Haas orbit in the resistivity of polycrystalline copper. [Preview Abstract] |
Tuesday, March 4, 2014 2:42PM - 2:54PM |
J46.00002: ABSTRACT WITHDRAWN |
Tuesday, March 4, 2014 2:54PM - 3:06PM |
J46.00003: Fermi liquid scaling of the optical conductivity in MnSi J. Steven Dodge, Laleh Mohtashemi, Amir Farahani, Eric Karhu, Theodore L. Monchesky We present measurements of the low-frequency optical conductivity of MnSi thin films made with time-domain terahertz spectroscopy. At low temperatures and low frequencies, the conductivity is consistent with the prediction of Fermi liquid theory, $\rho(\omega,T)\equiv [\sigma(\omega,T)]^{-1} = \rho_0 + A[(\hbar\omega)^2 + (2\pi k_B T)^2]$. As the temperature increases, the system loses quasi-particle coherence: deviations from Fermi liquid behavior appear, while the plasma frequency inferred from a Drude fit decreases dramatically. Above T$\approx 50$ K, $\sigma_2(\omega)$ develops a negative slope that indicates a sharp pseudogap in the conductivity spectrum. [Preview Abstract] |
Tuesday, March 4, 2014 3:06PM - 3:18PM |
J46.00004: A THz spectroscopic study of the heavy fermion CeFe$_2$Ge$_2$ Grace Bosse, Y. Li, L.H. Greene, J. Eckstein, N.P. Armitage We present time-domain THz spectroscopy data on a thin film of the heavy fermion compound CeFe$_2$Ge$_2$. Non-Fermi liquid behavior and a metamagnetic anomaly have been observed in CeFe$_2$Ge$_2$ pointing to its proximity to a quantum critical point, much like the well studied compounds CeNi$_2$Ge$_2$ and CeRu$_2$Si$_2$. A $T^{1.5}$ dependence of resistivity has been reported in the temperature range of 2K-15K. Our measurements to obtain the complex conductivity as a function of frequency were taken from room temperature down to 1.5K. Using this data in addition to DC resistivity measurements, we calculate the frequency dependent scattering rate using an extended Drude model analysis. The power law dependence of the scattering rate on frequency will be discussed in its relation to the anomalous transport properties that have been reported in this material. [Preview Abstract] |
Tuesday, March 4, 2014 3:18PM - 3:30PM |
J46.00005: ABSTRACT WITHDRAWN |
Tuesday, March 4, 2014 3:30PM - 3:42PM |
J46.00006: The Field-Temperature Phase Diagram of the Heavy Fermion Compound Ce$_2$Ge$_2$Mg William Gannon, Moosung Kim, Liusuo Wu, Meigan Aronson The heavy fermion metal Ce$_2$Ge$_2$Mg has a layered structure with the Ce nearest neighbor pairs arranged orthogonally to one another in the tetragonal $a$-$b$ plane, a structure topologically equivalent to the Shastry-Sutherland lattice (SSL). This material is thought to be more two dimensional than other $R_2T_2X$ SSL compounds such as Yb$_2$Pt$_2$Pb, due to the relatively long distance along the $c$-axis between Ce atoms in adjacent SSL planes. The magnetic phase diagram of Ce$_2$Ge$_2$Mg has been determined for magnetic fields in the SSL plane and along the $c$-axis, for temperatures from the antiferromagnetic transition at $T = 9.4$ K in zero applied field down to $T = 1.8$ K and fields as high as 14 T using magnetization, resistance, and heat capacity. Our measurements show a complex phase diagram with field suppressing the antiferromagnetic transition and the emergence of several ordered phases. These phases are possible evidence for singlet-to-triplet excitations in the Ce dimers. \\ This project was supported by NSF-DMR-1310008 [Preview Abstract] |
Tuesday, March 4, 2014 3:42PM - 3:54PM |
J46.00007: Strongly-disordered hybridization and non-Fermi liquid behavior in CePt$_4$Ge$_{12-x}$Sb$_x$ studied with thermoelectric power Benjamin White, Kevin Huang, M. Brian Maple Non-Fermi liquid (NFL) behavior is commonly associated with the presence of a nearby quantum critical point, but can also be observed in other scenarios. In a clean system, hybridization between localized and itinerant electron states can be characterized by a single Kondo temperature $T_K$, but introducing chemical disorder can lead to a wide distribution of $T_K$ values. Given sufficient disorder, the resulting distribution will tend to include an appreciable number of localized electron states which are characterized by $T_K \sim$ 0 K, and NFL behavior emerges. A Kondo-disorder type of NFL behavior was recently reported in the filled skutterudite system CePt$_4$Ge$_{12-x}$Sb$_x$ in the vicinity of $x = 1$. We performed a study of the thermoelectric power $S(T)$ for this system and observed an evolution of $S(T)$ with $x$ that is dramatic and broadly consistent with the boundaries of the proposed phase diagram. The effect of disordered hybridization is clearly observed in a low-temperature feature in $S(T)$ in the range $0.5 \le x \le 1.5$ and NFL behavior is also observed at x = 1. These results clearly demonstrate how sensitively $S(T)$ is able to probe a Kondo disorder system. [Preview Abstract] |
Tuesday, March 4, 2014 3:54PM - 4:06PM |
J46.00008: A percolation description of the critical behavior in quantum critical Ce(Ru0.24Fe0.76)Ge2 Tom Heitmann, John Gaddy, Wouter Montfrooij Quantum critical points (QCP) arise when the magnetic ordering of local moments that are embedding in a metallic system are just suppressed by Kondo shielding in the absence of thermal energy. Pure stoichiometric systems tend not to occur at QCPs so that an external tuning parameter is typically required to drive the system to the QCP. Often this external tuning parameter takes the form of chemical pressure by way of chemically substituting smaller (larger) ions at certain lattice positions such that the average interatomic spacing become smaller (larger). One unintended consequence of this approach, however, is the formation of a distribution of local interatomic---hence, also inter-moment---distances, which necessarily translates into a distribution of Kondo temperatures. In this case, the magnetic lattice fragments upon cooling such that percolation theory is necessary to describe the system, though---as we will demonstrate---certain modifications are required because of finite-size effects of the clusters. We argue that a complete QCP theory of heavily doped systems must begin by separating out the effects caused by the presence of magnetic clusters from those resulting from non-Fermi liquid behavior associated with the QCP. [Preview Abstract] |
Tuesday, March 4, 2014 4:06PM - 4:18PM |
J46.00009: Superconductivity in LaPd$_{1-x}$Bi$_{2}$ and moderate heavy fermion behavior in antiferromagnetic CePd$_{1-x}$Bi$_{2}$ Fei Han, Duck Young Chung, Mercouri Kanatzidis Superconductivity at 2.1 K is observed in LaPd$_{1-x}$Bi$_{2}$. A small residual resistance ratio indicates a strong scattering effect induced by Pd vacancies. Hall effect measurements reveal electron-like carriers and single-band transport behavior in LaPd$_{1-x}$Bi$_{2}$. Band structure calculations support the possibility of Fermi surface nesting near the fully stoichiometric case in LaPd$_{1-x}$Bi$_{2}$. By creating Pd vacancies the Fermi surface nesting is avoided which suppresses any potential CDW on the Bi net. CePd$_{1-x}$Bi$_{2}$ is non-superconducting but shows antiferromagnetic ordering below 6 K. A Sommerfeld coefficient of 0.199 J.molCe$^{-1}$K$^{-2}$ reveals a moderate heavy fermion behavior in CePd$_{1-x}$Bi$_{2}$. The resistivity curve shows the presence of Kondo and crystalline-electric-field effects. Magnetoresistance and Hall effect measurements show the interplay between Kondo and crystalline-electric-field effects obviously reconstructs the Fermi surface topology of CePd$_{1-x}$Bi$_{2}$ around 75 K. With the help of band structure calculations, we argue the f-d hybridization in CePd$_{1-x}$Bi$_{2}$ quenches the superconductivity. [Preview Abstract] |
Tuesday, March 4, 2014 4:18PM - 4:30PM |
J46.00010: Anomalous Hall Effect in Frustrated Kondo Lattices and Implications for Heavy Fermion System Pr$_2$Ir$_2$O$_7$ Wenxin Ding, Qimiao Si Pr$_2$Ir$_2$O$_7$ is a frustrated Kondo system that has a large zero field anomalous Hall Effect, which hints for a chiral spin liquid ground state of the local moments. Recently, thermodynamic measurements reveal a divergent Gr\"uneisen ratio, which indicates a nearby quantum critical point [1]. Motivated by these findings, we study the prototype chiral spin liquid state on the J1-J2 square lattice with Kondo coupling, and use it as a probe of the Kondo destruction quantum phase transition. For the Kondo screened phase, we study the topological properties of the hybridized heavy quasi-particle bands, and show that they yield a zero-field anomalous Hall effect. For the Kondo destroyed phase, we derived such Hall response by showing that the chiral spin liquids state mediates an effective chiral interaction among the electrons. The behavior of the Hall response on approach, and across, the quantum critical point is discussed based on these calculations. \\[4pt] [1] Y. Tokiwa et al, to be published (2013). [Preview Abstract] |
Tuesday, March 4, 2014 4:30PM - 4:42PM |
J46.00011: Magnetic structure of frustrated heavy fermion Yb$_2$Pt$_2$Pb Wojciech Miiller, Liusuo Wu, Jeffrey W. Lynn, Meigan C. Aronson Different realisations of frustrated magnetic systems attract a lot of interest due to the emergence of many exotic ground states where interplay of frustration and quantum effects is present. Among these systems, tetragonal Yb$_2$Pt$_2$Pb is believed to be a 4$f$ electron realisation of frustrated Shastry-Sutherland lattice (SSL), with antiferromagnetic order emerging below $T_N=$ 2.07 K [1] and where series of subsequent plateaus in the magnetisation suggests a complex magnetic phase diagram [2,3]. With neutron diffraction experiments we have found a solution of the magnetic structure of Yb$_2$Pt$_2$Pb that reproduces the magnetic intensities observed both in powder and single crystal data below $T_N$. The paramount finding is that this magnetic structure shows some features of classical 2D SSL lattice, where magnetic moments are confined within the tetragonal plane, as well as the presence of distinct antiferromagnetic dimers. There are indications as well that spin chain physics may be important. \\ This project was supported by NSF-DMR-1310008.\\ 1) Kim et al., Phys. Rev. B 77, 144425 (2008) \\ 2) Kim et al., PRL 110, 017201 (2013) \\ 2) Shimura et al., J. Phys. Soc. Jpn. 81, 103601 (2012)\\ [Preview Abstract] |
Tuesday, March 4, 2014 4:42PM - 4:54PM |
J46.00012: Wiedemann-Franz law and non-vanishing temperature scale across the field-tuned quantum critical point of YbRh$_2$Si$_2$ J.-Ph Reid, M. Tanatar, R. Daou, Rongwei Hu, C. Petrovic, Louis Taillefer The in-plane thermal conductivity $\kappa$ and electrical resistivity $\rho$ of the heavy-fermion metal YbRh$_2$Si$_2$ were measured down to 50 mK for magnetic fields $H$ parallel and perpendicular to the tetragonal $c$ axis, through the field-tuned quantum critical point, $H_c$, at which antiferromagnetic order ends. The thermal and electrical resistivities, $w \equiv L_0 T/\kappa$ and $\rho$, show a linear temperature dependence below 1~K, typical of the non-Fermi liquid behaviour found near antiferromagnetic quantum critical points, but this dependence does not persist down to $T=0$. Below a characteristic temperature $T^\star \simeq 0.35$~K, which depends weakly on $H$, $w(T)$ and $\rho(T)$ both deviate downward and converge as $T \to 0$. We propose that $T^\star$ marks the onset of short-range magnetic correlations, persisting beyond $H_c$. By comparing samples of different purity, we conclude that the Wiedemann-Franz law holds in YbRh$_2$Si$_2$, even at $H_c$, implying that no fundamental breakdown of quasiparticle behaviour occurs in this material. The overall phenomenology of heat and charge transport in YbRh$_2$Si$_2$ is similar to that observed in the heavy-fermion metal CeCoIn$_5$, near its own field-tuned quantum critical point. [Preview Abstract] |
Tuesday, March 4, 2014 4:54PM - 5:06PM |
J46.00013: Using Monte Carlo Ray tracing to Understand the Vibrational Response of UN as Measured by Neutron Spectroscopy J.Y.Y. Lin, A.A. Aczel, D.L. Abernathy, S.E. Nagler, W.J.L. Buyers, G.E. Granroth Recently neutron spectroscopy measurements, using the ARCS and SEQUOIA time-of-flight chopper spectrometers, [1] observed an extended series of equally spaced modes in UN that are well described by quantum harmonic oscillator behavior of the N atoms. Additional contributions to the scattering are also observed. Monte Carlo ray tracing simulations with various sample kernels have allowed us to distinguish between the response from the N oscillator scattering, contributions that arise from the U partial phonon density of states (PDOS), and all forms of multiple scattering. These simulations confirm that multiple scattering contributes an $\sim Q$-independent background to the spectrum at the oscillator mode positions. All three of the aforementioned contributions are necessary to accurately model the experimental data. These simulations were also used to compare the T dependence of the oscillator modes in SEQUOIA data to that predicted by the binary solid model [2].\\[4pt] [1] A. A. Aczel, {\it et al.}, Nat. comm. {\bf 3}, 1124 (2013).\\[0pt] [2] M. Warner, {\it et al.} Z. Phys. B {\bf 51}, 109 (1983) [Preview Abstract] |
Tuesday, March 4, 2014 5:06PM - 5:18PM |
J46.00014: $^{195}$Pt NMR measurements in the superconducting state of the nearly heavy Fermion metal U$_2$PtC$_2$ Andrew Mounce, G. Koutroulakis, H. Yasuoka, P. Ronning, E.D. Bauer, J.D. Thompson, N. Ni AC susceptibility and $^{195}$Pt nuclear magnetic resonance measurements of the nearly heavy Fermion metal U$_2$PtC$_2$, with $T_c(H_0=0) = 1.6$ K and $\gamma = 15$ mJ/mol$\cdot$ K$^2$,[1] were taken at temperature down to 10 mK and in magnetic fields up to 12 T. From AC susceptibility, an anisotropic $H_{c2}(T\approx 0)$ of 8 and 10 T has been measured with the external magnetic field $H_0\parallel c$ and $H_0\perp c$, respectively. Below $T_c$, the spectral shift is independent of temperature consistent with spin triplet electron pairing or large spin orbit coupling. Spin-lattice relaxation measurement at temperatures $T_{c} < T < 20$ K follow a modified Korringa relation which indicate ferromagnetic fluctuations, while below $T_c$, $1/T_1\propto T^2$ signifying unconventional superconductivity. [1] G. P. Meisner et al., PRL 53, 1829 (1984). [Preview Abstract] |
Tuesday, March 4, 2014 5:18PM - 5:30PM |
J46.00015: Two-band model of ferromagnetic $p$-wave superconductors Christopher L{\"o}rscher, Jingchuan Zhang, Qiang Gu, Richard Klemm We present results on the full angular and temperature dependencies of the upper critical induction, $B_{c2}(\theta,\phi,T)$, for a ferromagnetic $p$-wave completely broken symmetry state (CBS), in which parallel-spin electron pairing is pinned to only one crystal axis direction, $V(\hat{k},\hat{k}^{\prime})=V_{0}k_{z}k_{z}^{\prime}$, normal to the spontaneuous magnetization direction. We show that the angular dependence of $B_{c2}$ exhibits an anomalous peak at $\theta^{\star}<90^{\circ}$, due to a competition between order parameter anisotropy and effective mass anisotropy. We also propose a two-band model for ferromagnetic superconductors, where we have two ellipsoidal Fermi surfaces (FSs). Using this model, and by assuming a field-dependent anisotropic effective mass on one of the FSs, $m_{\uparrow,i}(B)$, we can fit the experimental data for the low-temperature specific heat $\gamma(B)$ of URhGe, which exhibits a peak at $\mu_0H\sim12$T in the $b$-axis direction. We provide quantitative fits to experiment, and propose that this model of a field-dependent effective mass can help to understand the reentrant phase of the ferromagnetic superconductor URhGe, and the upward curvature observed in $B_{c2}$ of UCoGe [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