Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session C27: Heavy Fermion Compounds: Experiment and Theory |
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Sponsoring Units: DCMP Chair: Sheng Ran, University of California, San Diego Room: 326 |
Monday, March 14, 2016 2:30PM - 2:42PM |
C27.00001: Global phase diagram and single particle excitations in Kondo insulators Qimiao Si, Jedediah Pixley, Rong Yu, Silke Paschen Motivated by quantum criticality in Kondo insulators [1] tuned by pressure or doping we study the effects of magnetic frustration and the properties of the single particle excitations in a Kondo lattice model [2]. Focusing on the Kondo insulating limit we study the Shastry-Sutherland Kondo lattice and determine the zero temperature phase diagram, which incorporates a valence bond solid, antiferromagnet, and Kondo insulating ground states, with metal-to-insulator quantum phase transitions. We argue that this phase diagram is generic and represents a ``global'' phase diagram of Kondo insulators in terms of quantum fluctuations and the Kondo interaction. We then focus on the momentum distribution of single particle excitations within the Kondo insulating ground state. We show how features of the Fermi-surface of the underlying conduction electrons appear in the Kondo insulating phase. Lastly, we discuss the implications of our results for quantum criticality in Kondo~insulators [1] as well as for the recent de Haas-von Alphen measurements in the Kondo insulator SmB6 [3,4]. [1] Q. Si and S. Paschen, physica status solidi (b) 250, 425 (2013). [2] J. H. Pixley, et. al., arXiv:1509.02907 (2015). [3] B. Tan et al, Science 349, 287 (2015). [4] G. Li et al, Science 346, 1208 (2014). [Preview Abstract] |
Monday, March 14, 2016 2:42PM - 2:54PM |
C27.00002: Probing the Kondo State using Terahertz Radiation Christoph Wetli, Johann Kroha, Cornelius Krellner, Kristin Kliemt, Oliver Stockert, Hilbert v. Loehneysen, Manfred Fiebig The appearance of quantum critical phase transitions is boosting the interest in the field of Kondo-lattice systems. After intense research over the last decades, experimental insights have been mainly gained by measuring the specific heat capacity or the magnetic susceptibility and relating them to the increase of the effective mass. Lately, it has been demonstrated that ARPES experiments allow direct access to the electrons contributing to the Kondo-lattice effect, but with some experimental restrictions. We will show that THz radiation is a powerful and highly accurate alternative for investigating the approach to the coherent Kondo-state of heavy-fermion systems. Photons in the THz range directly couple to the electronic heavy quasiparticles causing the Kondo-singlet behavior. Additionally, this technique allows studying Kondo-state dynamics on the picosecond time scale. We report lifetime measurements of excited Kondo singlets for the two crystalline rare earth heavy-fermion systems CeCu$_6$ and YbRh$_2$Si$_2$, where the lifetimes scale inversely proportional to the Kondo-temperature. THz spectroscopy thus gives a very different perspective towards the Kondo-lattice effect, with the unique ability to combine temporal resolution and possible measurements in magnetic field. [Preview Abstract] |
Monday, March 14, 2016 2:54PM - 3:06PM |
C27.00003: ABSTRACT WITHDRAWN |
Monday, March 14, 2016 3:06PM - 3:18PM |
C27.00004: Emergence of anisotropic heavy fermions in antiferromagnetic Kondo lattice CeIn$_{\mathrm{3}}$ revealed by photoemission Yun Zhang, Haiyan Lu, Xiegang Zhu, Shiyong Tan, Qiuyun Chen, Wei Feng, Donghua Xie, Lizhu Luo, Wen Zhang, Xinchun Lai One basic concept in heavy fermions systems is the entanglement of localized spin state and itinerant electron state. It can be tuned by two competitive intrinsic mechanisms, Kondo effect and Ruderman-Kittel-Kasuya-Yosida interaction, with external disturbances. The key issue regarding heavy fermions properties is how the two mechanisms work in the same phase region. To investigate the relation of the two mechanisms, the cubic antiferromagnetic heavy fermions compound CeIn$_{\mathrm{3}}$ was investigated by soft x-ray angle resolved photoemission spectroscopy. The hybridization between f electrons and conduction bands in the paramagnetic state was observed directly, providing compelling evidence for Kondo screening scenario and coexistence of two mechanisms. The hybridization strength shows slight and regular anisotropy in K space, implying that the two mechanisms are competitive and anisotropic. This work illuminates the concomitant and competitive relation between the two mechanisms and supplies some evidences for the anisotropic superconductivity of CeIn$_{\mathrm{3}}$ [Preview Abstract] |
Monday, March 14, 2016 3:18PM - 3:30PM |
C27.00005: Global phase diagram of the Ising-anisotropic Kondo lattice Emilian M Nica, Kevin Ingersent, Qimiao Si In recent years, a significant amount of work has been dedicated to understanding heavy-fermion quantum criticality. What has emerged is a proposed global phase diagram [1] meant to capture the interplay between Kondo singlet formation, magnetic ordering and intrinsic fluctuations associated with the quantum-mechanical nature of the local moments. Using an Extended Dynamical Mean-Field Theory (EDMFT) approach, we study a prototypical Ising-anisotropic Kondo lattice model in the presence of a transverse field that provides a way of controlling the quantum fluctuations of the local moments. We show that the transverse field opens up a line of continuous transitions directly from an antiferromagnetic phase with Kondo destruction (and, hence, a small Fermi surface) to a paramagnetic heavy-fermion state (with a large Fermi surface). We show that the critical scaling characteristics along this line are the same as for the previously studied zero-transverse field case, indicating the robustness of the Kondo-destruction scenario with respect to enhanced quantum fluctuations. General implications of our results for the global phase diagram and heavy-fermion quantum criticality will be discussed. [1] ``Kondo Destruction and Quantum Criticality in Kondo Lattice Systems,'' Q. Si, J. H. Pixley, E. Nica, S. J. Yamamoto, P. Goswami, R. Yu, and S. Kirchner, J. Phys. Soc. Jpn. \textbf{83, }061005 (2014). [Preview Abstract] |
Monday, March 14, 2016 3:30PM - 3:42PM |
C27.00006: Spin wave spectrum in CeRhIn$_5$ under applied magnetic fields David Fobes, S.-Z. Lin, N.J. Ghimire, F. Ronning, E.D. Bauer, J.D. Thompson, C.D. Batista, G. Ehlers, M. Janoschek The phase diagram of CeRhIn$_5$ is in many ways a prototypical example of a heavy fermion superconductor; it is a heavy fermion antiferromagnet that can be tuned to a quantum critical point (QCP) via pressure, around which unconventional superconductivity emerges. Closer inspection reveals unusual behavior however; the interplay between magnetism and unconventional superconductivity is atypical, and electrical transport behavior and changes in the Fermi surface at the QCP are not in agreement with the prototypical spin-density-wave-type scenario. This is supported by our previous measurements of the spin wave spectrum at ambient pressure replicated by a simple frustrated $J_1-J_2$ model based on localized Ce $4f$ electrons. We show that the addition of magnetic anisotropy and Zeeman terms to our Anisotropic Next-Nearest Neighbor Ising (ANNNI) model Hamiltonian quantitatively describes the spin wave spectrum under the application of magnetic field as obtained by neutron scattering, and reproduces the experimental magnetic phase diagram. Finally, this model predicts that the magnetic ordering vector should change logarithmically as a function of temperature across the high-field incommensurate-to-commensurate phase boundary, in agreement with our latest neutron diffraction results. [Preview Abstract] |
Monday, March 14, 2016 3:42PM - 3:54PM |
C27.00007: An efficient continuous-time quantum Monte Carlo impurity solver in Kondo Regime Changming Yue, Yilin Wang, Xi Dai An efficient continuous-time quantum Monte Carlo impurity solver with high acceptation ratio at low temperature is developed to study the strongly correlated heavy-fermion materials. In this solver, the imaginary time evolution operator for the high energy multiplets, which decays very rapidly with time, is approximated by a $\delta$ function, and as a result the virtual charge fluctuations of $f^n \rightarrow f^{n \pm 1}$ are all included without applying Schrieffer-Wolff transformation explicitly . As benchmarks, our algorithm perfectly reproduces the results for both Coqblin-Schriffeer and Kondo lattice models obtained by ct-$J$ method developed by Junya Otsuki et al. Furthermore, it allows us to study low energy physics of heavy-fermion materials directly without fitting the exchange coupling $J$ in the Kondo model. As an example, we test our solver on CeCoIn5, the famous heavy fermion material within the framework of LDA+DMFT to obtain its quasi-particle spectrum. [Preview Abstract] |
Monday, March 14, 2016 3:54PM - 4:06PM |
C27.00008: Investigation of quantum criticality in the new heavy fermion compound Ce$_{\mathrm{2}}$PdAl$_{\mathrm{7}}$Ge$_{\mathrm{4}}$ Eric Bauer, N. A. Wakeham, D. Kim, N. J. Ghimire, F. Ronning, R. Movshovich, J. D. Thompson Ce-based intermetallic compounds exhibit a variety of interesting ground states including magnetic order, heavy fermion behavior, unconventional superconductivity, and non-Fermi liquid behavior. When magnetic order is suppressed to T$=$ 0 K, or quantum critical point, by chemical substitution, pressure, or magnetic field, a dome of unconventional superconductivity is often found. Close to the quantum critical point, non-Fermi liquid temperature dependencies of the thermodynamic and transport properties are observed. ~ Recently, a new family of tetragonal Ce$_{\mathrm{2}}$MAl$_{\mathrm{7}}$Ge$_{\mathrm{4}}$ (M$=$Co, Ni, Pd, Ir) compounds was discovered. While the Ce$_{\mathrm{2}}$MAl$_{\mathrm{7}}$Ge$_{\mathrm{4}}$ (M$=$Co, Ir, Ni) materials order magnetically between T$_{\mathrm{m}}=$0.8 - 1.6 K, Ce$_{\mathrm{2}}$PdAl$_{\mathrm{7}}$Ge$_{\mathrm{4}}$ exhibits non-Fermi liquid behavior at low temperature. Here, we discuss the quantum criticality in Ce$_{\mathrm{2}}$PdAl$_{\mathrm{7}}$Ge$_{\mathrm{4}}$. [Preview Abstract] |
Monday, March 14, 2016 4:06PM - 4:18PM |
C27.00009: Fermiology Of Ce2Rh3Ge5 Mark Wartenbe The competition between localized and delocalized f electrons in heavy fermion materials produces a wide variety of interesting physical phenomena. Among these compounds is Ce2Rh3Ge5. This heavy-fermion system undergoes an antiferromagnetic transition below 4K and exhibits an angle dependent magnetic phase transition around 25 tesla. In addition, RF conductivity measurements in pulsed field (65T) have revealed quantum oscillations. Temperature dependence at fixed angle indicates relatively heavy effective masses of values ranging from \textasciitilde 3m$_{\mathrm{e}}$ on up to \textasciitilde 10m$_{\mathrm{e}}$. This indicates that the narrow f-electron density of states is partially hybridized close to the Fermi energy, but also places strict cryogenic constraints upon the measurement ( $^{\mathrm{3}}$Helium temperatures are required). Fermi surface calculations have produced complex figures which lend validation to such rich behavior. Presented are updated measurements including magnetization and revised theoretical calculations.. [Preview Abstract] |
Monday, March 14, 2016 4:18PM - 4:30PM |
C27.00010: Investigation of the physical properties of the new heavy fermion compounds Ce$_{\mathrm{2}}$MAl$_{\mathrm{7}}$Ge$_{\mathrm{4}}$ (M $=$ Co, Ir, Ni, Pd) Nirmal Ghimire, Samantha Cary, Thomas Albrecht-Schmitt, Craig Brown, Serena Eley, Nicholas Wakeham, Priscila Rosa, Marc Janoschek, Leonardo Civale, Joe Thompson, Filip Ronning, Eric Bauer Ce-based intermetallic compounds provide a fascinating ground to study several exotic physical phenomena due to the presence of competing low Kondo and RKKY interactions.~ One widely explored entity in these compounds is the quantum phase transition that is accessed by the suppression of the magnetic order down to absolute temperature by an external parameter such as magnetic field, chemical substitution, or pressure. Exotic phenomena like unconventional superconductivity and non-Fermi liquid behavior are ubiquitous in the vicinity of the quantum critical point.~ Quantum criticality in these Ce-based materials is often observed in layered, tetragonal systems such as the CeM$_{\mathrm{2}}$X$_{\mathrm{2}}$ (M$=$transition metal; X$=$Si, Ge) or CeMIn$_{\mathrm{5}}$ (M$=$Co, Rh, Ir) compounds. We present the structural and physical properties of a new family of heavy fermion compounds Ce$_{\mathrm{2}}$MAl$_{\mathrm{7}}$Ge$_{\mathrm{4}}$ (M $=$ Co, Ir, Ni, Pd) that crystallize in the tetragonal space group P-42$_{\mathrm{1}}$m. Ce$_{\mathrm{2}}$MAl$_{\mathrm{7}}$Ge$_{\mathrm{4}}$ (M$=$Co, Ir, Ni) show complex magnetic order below 2 K, while Ce$_{\mathrm{2}}$PdAl$_{\mathrm{7}}$Ge$_{\mathrm{4}}$ does not order magnetically down to 400 mK, and, instead, shows quantum critical behavior at low temperature. [Preview Abstract] |
Monday, March 14, 2016 4:30PM - 4:42PM |
C27.00011: Antiferromagnetic Kondo lattice in the layered compounds Re$_{2}$NiGa$_{9}$Ge$_{2}$ (Re$=$Ce, Pr, Sm) Yanglin Zhu, Jinyu Liu, Jin Hu, Daniel Adams, Leonard Spinu, Zhiqiang Mao Intermetallic compounds containing rare-earth/actinide elements with 4f/5f electrons have formed a special family of strongly correlated materials, i.e. heavy fermion systems. We have recently found a new layered rare earth intermetallic system showing moderate heavy fermion behavior: Re$_{2}$NiGa$_{9}$Ge$_{2}$ (Re$=$Ce, Sm, Pr). The Re$=$Ce and Sm members were previously synthesized [1], while their electronic properties have not been reported. We have recently grown single crystals of Re$_{2}$NiGa$_{9}$Ge$_{2}$ (Re$=$Ce, Sm, Pr) and characterized their electronic and magnetic properties. We find all these materials are antiferromagnetic, with T$_{N} \quad =$2.5 K, 5 K, 3.4 K respectively for Re$=$Ce, Pr and Sm. Moreover, they also exhibit large values of electronic specific coefficient: $\gamma \approx $101 mJ mol-Ce$^{-1}$ K$^{-2}$ for Re$=$Ce, 368 mJ mol-Pr$^{-1}$ K$^{-2}$ for Re$=$Pr, and 196.4 mJ mol-Sm$^{-1}$ K$^{-2}$ for Re$=$Sm, indicating enhanced Kondo effect and the presence of AFM Kondo lattice. Our findings suggest that Re$_{2}$NiGa$_{9}$Ge$_{2}$ (Re$=$Ce, Pr, Sm) could be interesting candidate materials for exploring novel exotic properties of correlated electrons through external parameter tuning such as chemical substitution and pressure. Reference: [1] M. A. Zhuravleva and M. G. Kanatzidis, Inorg. Chem. 2008, 47 (20), 9471-9477. [Preview Abstract] |
Monday, March 14, 2016 4:42PM - 4:54PM |
C27.00012: High-resolution x-ray diffraction study of the heavy-fermion compound YbBiPt B. G. Ueland, S. M. Saunders, S. L. Bud'ko, G. M. Schmiedeshoff, P. C. Canfield, A. Kreyssig, A. I. Goldman YbBiPt is a heavy-fermion compound possessing significant short-range antiferromagnetic correlations below $T^{\rm{*}}=0.7$~K, fragile antiferromagnetic order below $T_{\rm{N}}=0.4$~K, a Kondo temperature of $T_{\rm{K}} \approx1$~K, and crystalline-electric-field splitting (CEF) on the order of $E/k_{\rm{B}}=1\,\rm{-}\,10$~K. Its lattice is face-centered cubic at ambient temperature, but certain data, particularly those from studies aimed at determining the CEF level scheme, suggest that the lattice distorts at lower temperature. Here, we present results from high-energy x-ray diffraction experiments which show that, within our experimental resolution of $\approx6\,\rm{-}\,10\times10^{-5}$~\AA, no structural phase transition occurs between $1.5 $ and $50$~K. Despite this result, we demonstrate that the compound's thermal expansion may be modeled using CEF level schemes appropriate for Yb$^{3+}$ residing on a site with either cubic or less than cubic point symmetry.\\Work at the Ames Laboratory was supported by the US DOE, BES, DMSE, under Contract No. DE-AC02-07CH11358. Work at Occidental College was supported by the NSF under DMR-1408598. This research used resources at the Advanced Photon Source a US DOE, Office of Science, User Facility. [Preview Abstract] |
Monday, March 14, 2016 4:54PM - 5:06PM |
C27.00013: Intermediate valence to heavy fermion through a quantum phase transition in Yb$_3$(Rh$_{1-x}T_x$)$_4$Ge$_{13}$ (${T}$ = Co, Ir) single crystals Binod Rai, Emilia Morosan Single crystals of Yb${_3}$(Rh$_{1-x}$$T$$_x$)${_4}$Ge$_{13}$ ($T$ = Co, Ir) have been grown using the self-flux method. Powder X-ray diffraction data on these compounds are consistent with the cubic structure with space group $Pm\bar{3}n$. Intermediate valence behavior is observed in Yb${_3}$(Rh$_{1-x}$$T$$_x$)${_4}$Ge$_{13}$ upon $T$ = Co doping, while $T$ = Ir doping drives the system into a heavy fermion state. Antiferromagnetic order is observed in the Ir-doped samples Yb${_3}$(Rh$_{1-x}$$T$$_x$)${_4}$Ge$_{13}$ for 0.5 $<$ $x$ $\leq$ 1 with T$_N$ = 0.96 K for Yb${_3}$Ir${_4}$Ge$_{13}$. With decreasing $x$, the magnetic order is suppressed towards a quantum critical point around $x_c$ = 0.5, accompanied by non-Fermi liquid behavior evidenced by logarithmic divergence of the specific heat and linear temperature dependence of the resistivity. The Fermi liquid behavior is recovered with the application of large magnetic fields. [Preview Abstract] |
Monday, March 14, 2016 5:06PM - 5:18PM |
C27.00014: Electronic and Magnetic Properties of Cd-Doped PuRhIn5 Jian-Xin Zhu Since their discovery nearly a decade ago, plutonium-based superconductors have attracted considerable interest, which is now heightened by the latest discovery of superconductivity in other Pu-115 compounds. Within the generalized gradient approximation (GGA) of density functional theory and its combination with the dynamical mean-field theory, we present a study of electronic structure in the paramagnetic state of Cd-doped PuRhIn$_5$. A doping-induced delocalization-localization transition is identified. In addition, the spin-polarized GGA-based total energy calculations are performed to determine the magnetic exchange interactions in the pristine PuRhIn$_5$. The implication to the nature of quantum criticality is discussed. [Preview Abstract] |
Monday, March 14, 2016 5:18PM - 5:30PM |
C27.00015: Phenomenological Magnetic Model in Tsai-Type Approximants Takanori Sugimoto, Takami Tohyama, Takanobu Hiroto, Ryuji Tamura Recent neutron diffraction study has reported a curious ferromagnetism in Tsai-type approximants Au-Si-RE (RE=Tb,Dy,Ho), which have the same local structure as quasi-crystals with a translational symmetry simultaneously. In these materials, magnetic moments of rare-earth atoms have a single-ion anisotropy determined locally via spin-orbit coupling around crystal fields satisfying a distorted icosahedral crystal structure. We phenomenologically propose a possible magnetic model reproducing the magnetic structure and the thermodynamical quantities. The corresponding energies of the single-ion anisotropy and RKKY exchange couplings are also estimated by comparing magnetization curves and susceptibility of our model and experiments. Moreover, simulated annealing calculations with the energies in our model coincide with the strange ferromagnetism. In conclusion, a distortion of icosahedral cluster in body-centered cubic structure plays a key role to emerge the peculiar magnetic structure. Our magnetic model does not only explain magnetic behaviors in quasi-crystal approximants, but also can approach to a coexistence of a long-ranged order and a quasi-periodicity. [Preview Abstract] |
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