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C. Geibel - One of the best experts on this subject based on the ideXlab platform.

  • 29si nmr study of the Heavy Fermion System cerusi
    Journal of Physics: Conference Series, 2010
    Co-Authors: R Sarkar, M Baenitz, J G Sereni, C. Geibel
    Abstract:

    A recent investigation of the low temperature properties of the paramagnetic Heavy Fermion System CeRuSi revealed an anomalous decrease of the coefficient C/T below 6 K, indicating a second low energy scale well below the Kondo temperature of about 50 K. We started an investigation of this unusual behavior using the local probe 29Si-NMR. Here a preliminary 29Si field sweep NMR study in the temperature 4.2-200 K is reported. 29Si-NMR powder spectra obtained at 72.9 MHz could be simulated and shift components 29Kab(T) and 29Kc(T) were determined. The shift along the basal plane 29Kab(T) shows the expected behavior with a Curie-Weiss dependence at high T merging in a constant value below 15 K. In contrast the shift along the tetragonal axis reveals an anomalous T dependence below 15 K where 29Kc(T) drops by a factor of 2, confirming the presence of a further low T energy scale. We suspect this drop to be related to the anomalous decrease of C/T below 6 K and discuss possible mechanism.

  • evidence for a metamagnetic transition in the Heavy Fermion System cetige
    Journal of Physics: Conference Series, 2010
    Co-Authors: M Deppe, N Carocacanales, J G Sereni, C. Geibel
    Abstract:

    A recent study of CeTiGe identified this compound as a paramagnetic Heavy Fermion System where the full J = 5/2 multiplet is involved in the formation of the ground state. Here we present a preliminary investigation of the dc-magnetization Mdc(H) and of the magnetoresistance ?(H) of polycrystalline CeTiGe samples in applied magnetic fields up to ?0H = 14 T. The results reveal a pronounced metamagnetic transition at a critical field ?0Hc ? 13.5 T at low temperatures, with a step like increase in Mdc(H) of at least 0.6 ?B/Ce. The metamagnetic transition leads to a strong decrease in ?(H). A clear hysteresis in Mdc(H) and ?(H) indicate that in CeTiGe these metamagnetic features correspond to a true thermodynamic, first order type transition in contrast to the critical behavior observed in the canonical System CeRu2Si2. Measurements at higher temperatures showed a continuous suppression of the metamagnetic transition with increasing T, which vanishes at T ~ 30 K.

  • Tuning the hybridization at the surface of a Heavy-Fermion System.
    Physical review letters, 2009
    Co-Authors: Denis V. Vyalikh, C. Geibel, Steffen Danzenbächer, Yu. Kucherenko, Cornelius Krellner, Clemens Laubschat, M. Shi, Luc Patthey, R. Follath, S. L. Molodtsov
    Abstract:

    Electron-hybridization phenomena in YbRh_{2}Si_{2} were probed by angle-resolved photoemission. It was shown that the Yb 4f-Rh 4d hybridization strength in the surface region of this Heavy-Fermion material can be varied by deposition of Ag. Site-specific charge transfer from adatoms leads to change of the energy overlap of the interacting states close to the Fermi energy. Our study demonstrates a new way to tune the hybridization between 4f and valence electrons as well as the induced strong correlation effects at the surface of Heavy-Fermion Systems.

  • new non magnetically ordered Heavy Fermion System cetige
    Journal of Physics: Condensed Matter, 2009
    Co-Authors: M Deppe, N Carocacanales, Stefanie Hartmann, N Oeschler, C. Geibel
    Abstract:

    Investigations of the susceptibility, electrical resistivity, specific heat and thermopower of CeTiGe at low temperatures show that this compound is a Kondo lattice System with an enhanced Sommerfeld coefficient γ≈0.3 J K−2 mol−1 and where the whole J = 5/2 multiplet is involved in the formation of the ground state. No magnetic order was observed down to 0.4 K. In the temperature range below 10 K we observed Fermi-liquid behavior as indicated by a ρ(T)~T2 dependence in the electrical resistivity and a linear specific heat and thermopower. Because of these results we classify CeTiGe as a moderate Heavy-Fermion System with a non-magnetic ground state.

  • investigation of yb2pt6al15 single crystals Heavy Fermion System with a large local moment degeneracy
    New Journal of Physics, 2008
    Co-Authors: M Deppe, Stefanie Hartmann, N Oeschler, M Nicklas, M E Macovei, C. Geibel
    Abstract:

    We grew single crystals of Yb2Pt6Al15 and investigated the magnetic properties of this compound by means of susceptibility ?(T), specific heat C(T), resistivity ? (T) and thermoelectric power S(T) measurements. While all properties follow in general the behavior typical for Kondo-lattice Systems, ?(T) and C(T)/T present broad maxima in the T range 17?35?K, which matches nicely the prediction of the Coqblin?Schrieffer model for J= 7/2. A large degeneracy of the local moment is also supported by a reduced Kadowaki?Woods ratio. Thus, the analysis of all investigated properties evidences Yb2Pt6Al15 to be a paramagnetic Kondo-lattice System with the whole J= 7/2 multiplet involved in the formation of the Kondo state, a Kondo temperature of the order of 60?K, and a Heavy Fermi-liquid ground state with a Sommerfeld coefficient ? 0 = 0.33?J?(mol-Yb)?1?K?2 corresponding to a mass enhancement of the order of 30.

F. Steglich - One of the best experts on this subject based on the ideXlab platform.

  • pronounced first order metamagnetic transition in the paramagnetic Heavy Fermion System cetige
    Physical Review B, 2012
    Co-Authors: M Deppe, N Carocacanales, Stefan Lausberg, Franziska Weickert, M Brando, Yurii Skourski, Chistoph Geibel, F. Steglich
    Abstract:

    We report on the observation of large, steplike anomalies in the magnetization ($\ensuremath{\Delta}M=0.74\phantom{\rule{0.28em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}/$Ce), in the magnetostriction ($\ensuremath{\Delta}l/{l}_{0}=2.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$), and in the magnetoresistance in polycrystals of the paramagnetic Heavy-Fermion System CeTiGe at a critical magnetic field ${\ensuremath{\mu}}_{0}{H}_{c}\ensuremath{\approx}12$ T at low temperatures. The size of these anomalies is much larger than those reported for the prototypical Heavy-Fermion metamagnet CeRu${}_{2}$Si${}_{2}$. Furthermore, hysteresis between increasing and decreasing field data indicate a real thermodynamic, first-order type of phase transition, in contrast to the crossover reported for CeRu${}_{2}$Si${}_{2}$. Analysis of the resistivity data shows a pronounced decrease of the electronic quasiparticle mass across ${H}_{c}$. These results establish CeTiGe as a rare metamagnetic Kondo-lattice System, with an exceptionally large, metamagnetic transition of first-order type at a moderate field.

  • hall effect measurements in the Heavy Fermion System ceirin5
    Physica B-condensed Matter, 2008
    Co-Authors: Sunil Nair, F. Steglich, S Wirth, M Nicklas, A Gladun, J L Sarrao, J D Thompson
    Abstract:

    Abstract Sensitive Hall effect measurements are reported on single crystal specimens of the Heavy Fermion superconductor CeIrIn5 down to 0.05 K and magnetic fields up to 9 T. The measured Hall resistivities ρxy(H) are nonlinear down to lowest temperatures. The differential Hall coefficient is compared with both the Co counterpart as well as their non-magnetic analogues.

  • quantum criticality in the cubic Heavy Fermion System cein3 xsnx
    Physical Review Letters, 2006
    Co-Authors: R Kuchler, C. Geibel, N Carocacanales, J G Sereni, P Gegenwart, J Custers, O Stockert, F. Steglich
    Abstract:

    We report a comprehensive study of ${\mathrm{CeIn}}_{3\ensuremath{-}x}{\mathrm{Sn}}_{x}$ ($0.55\ensuremath{\le}x\ensuremath{\le}0.8$) single crystals close to the antiferromagnetic quantum-critical point (QCP) at ${x}_{c}\ensuremath{\approx}0.67$ by means of the low-temperature thermal expansion and Gr\"uneisen parameter. This System represents the first example for a cubic Heavy Fermion in which ${T}_{N}$ can be suppressed continuously down to $T=0$. A characteristic sign change of the Gr\"uneisen parameter between the antiferromagnetic and paramagnetic states indicates the accumulation of entropy close to the QCP. The observed quantum-critical behavior is compatible with the predictions of the itinerant theory for three-dimensional critical spin fluctuations. This has important implications for the role of the dimensionality in Heavy-Fermion QCPs.

  • low temperature properties of the Heavy Fermion System ybir2si2
    Physica B-condensed Matter, 2006
    Co-Authors: Z Hossain, C. Geibel, Franziska Weickert, T Radu, Y Tokiwa, C Krellner, H S Jeevan, P Gegenwart, F. Steglich
    Abstract:

    Abstract We report here the magnetic susceptibility, specific heat and electrical resistivity on high-quality single crystals of YbIr 2 Si 2 . It crystallizes either in the I-type body-centered ThCr 2 Si 2 or P-type CaBe 2 Ge 2 structure. P-type sample orders magnetically below 0.7 K whereas the I-type System remains paramagnetic down to 40 mK and shows Heavy Fermion behavior. Low-temperature resistivity and specific heat of this compound has strong similarity with YbRh 2 Si 2 down to 400 mK. However, below 200 mK YbIr 2 Si 2 attains Fermi-liquid ground state in contrast to YbRh 2 Si 2 which shows non-Fermi-liquid behavior.

  • hall effect measurements in the Heavy Fermion System cecoin5 escholarship
    Physica B-condensed Matter, 2006
    Co-Authors: Sanjay Singh, F. Steglich, S Wirth, M Nicklas, A Gladun, M Rams, Hanoh Lee, Z Fisk
    Abstract:

    Hall effect measurements have been conducted on high-quality single crystals of the Heavy-Fermion superconductor CeCoIn5. The anomalous Hall contribution is negligible in the investigated temperature range from 0.05 to 5 K. The measured Hall resistivities ρxy show a noticeable change in slope between the low-field (initial Hall coefficient) and the high-field region. In the superconducting regime, T Hc 2, the upper critical field of superconductivity. The high-field Hall coefficient is almost constant for temperatures down to 250 mK. At T {less-than or slanted equal to} 250 mK, an additional change in curvature of ρxy vs. H is observed. © 2006 Elsevier B.V. All rights reserved.

Yoshiteru Maeno - One of the best experts on this subject based on the ideXlab platform.

  • superconductivity and quantum criticality in the Heavy Fermion System beta ybalb4
    Nature Physics, 2008
    Co-Authors: Satoru Nakatsuji, Kentaro Kuga, Y Machida, Takashi Tayama, Toshiro Sakakibara, Yoshitomo Karaki, H Ishimoto, Shingo Yonezawa, Yoshiteru Maeno
    Abstract:

    A long-sought ytterbium-based Heavy-Fermion superconductor—a hole analogue of the cerium-based Systems—has been found. Moreover, there is evidence for a quantum critical point at ambient conditions and without chemical doping. A long-standing question in the field of superconductivity is whether pairing of electrons can arise in some cases as a result of magnetic interactions instead of electron–phonon-induced interactions as in the conventional Bardeen–Cooper–Schrieffer theory1. A major challenge to the idea of magnetically mediated superconductivity has been the dramatically different behaviour of the cerium and ytterbium Heavy-Fermion compounds. The cerium-based Systems are often found to be superconducting1,2,3,4,5,6, in keeping with a magnetic pairing scenario, but corresponding ytterbium Systems, or hole analogues of the cerium Systems, are not. Despite searches over two decades there has been no evidence of Heavy-Fermion superconductivity in an ytterbium System, casting doubt on our understanding of the electron–hole parallelism between the cerium and the ytterbium compounds. Here we present the first empirical evidence that superconductivity is indeed possible in an ytterbium-based Heavy-Fermion System. In particular, we observe a superconducting transition at Tc=80 mK in high-purity single crystals of YbAlB4 in the new structural β phase7. We also observe a novel type of non-Fermi-liquid state above Tc that arises without chemical doping, in zero applied magnetic field and at ambient pressure, establishing β-YbAlB4 as a unique System showing quantum criticality without external tuning.

  • superconductivity and quantum criticality in the Heavy Fermion System beta ybalb4
    Nature Physics, 2008
    Co-Authors: Satoru Nakatsuji, Kentaro Kuga, Y Machida, Takashi Tayama, Toshiro Sakakibara, Yoshitomo Karaki, H Ishimoto, Shingo Yonezawa, Yoshiteru Maeno
    Abstract:

    A long-sought ytterbium-based Heavy-Fermion superconductor—a hole analogue of the cerium-based Systems—has been found. Moreover, there is evidence for a quantum critical point at ambient conditions and without chemical doping.

Kentaro Kuga - One of the best experts on this subject based on the ideXlab platform.

  • superconductivity and quantum criticality in the Heavy Fermion System beta ybalb4
    Nature Physics, 2008
    Co-Authors: Satoru Nakatsuji, Kentaro Kuga, Y Machida, Takashi Tayama, Toshiro Sakakibara, Yoshitomo Karaki, H Ishimoto, Shingo Yonezawa, Yoshiteru Maeno
    Abstract:

    A long-sought ytterbium-based Heavy-Fermion superconductor—a hole analogue of the cerium-based Systems—has been found. Moreover, there is evidence for a quantum critical point at ambient conditions and without chemical doping. A long-standing question in the field of superconductivity is whether pairing of electrons can arise in some cases as a result of magnetic interactions instead of electron–phonon-induced interactions as in the conventional Bardeen–Cooper–Schrieffer theory1. A major challenge to the idea of magnetically mediated superconductivity has been the dramatically different behaviour of the cerium and ytterbium Heavy-Fermion compounds. The cerium-based Systems are often found to be superconducting1,2,3,4,5,6, in keeping with a magnetic pairing scenario, but corresponding ytterbium Systems, or hole analogues of the cerium Systems, are not. Despite searches over two decades there has been no evidence of Heavy-Fermion superconductivity in an ytterbium System, casting doubt on our understanding of the electron–hole parallelism between the cerium and the ytterbium compounds. Here we present the first empirical evidence that superconductivity is indeed possible in an ytterbium-based Heavy-Fermion System. In particular, we observe a superconducting transition at Tc=80 mK in high-purity single crystals of YbAlB4 in the new structural β phase7. We also observe a novel type of non-Fermi-liquid state above Tc that arises without chemical doping, in zero applied magnetic field and at ambient pressure, establishing β-YbAlB4 as a unique System showing quantum criticality without external tuning.

  • superconductivity and quantum criticality in the Heavy Fermion System beta ybalb4
    Nature Physics, 2008
    Co-Authors: Satoru Nakatsuji, Kentaro Kuga, Y Machida, Takashi Tayama, Toshiro Sakakibara, Yoshitomo Karaki, H Ishimoto, Shingo Yonezawa, Yoshiteru Maeno
    Abstract:

    A long-sought ytterbium-based Heavy-Fermion superconductor—a hole analogue of the cerium-based Systems—has been found. Moreover, there is evidence for a quantum critical point at ambient conditions and without chemical doping.

Satoru Nakatsuji - One of the best experts on this subject based on the ideXlab platform.

  • superconductivity and quantum criticality in the Heavy Fermion System beta ybalb4
    Nature Physics, 2008
    Co-Authors: Satoru Nakatsuji, Kentaro Kuga, Y Machida, Takashi Tayama, Toshiro Sakakibara, Yoshitomo Karaki, H Ishimoto, Shingo Yonezawa, Yoshiteru Maeno
    Abstract:

    A long-sought ytterbium-based Heavy-Fermion superconductor—a hole analogue of the cerium-based Systems—has been found. Moreover, there is evidence for a quantum critical point at ambient conditions and without chemical doping. A long-standing question in the field of superconductivity is whether pairing of electrons can arise in some cases as a result of magnetic interactions instead of electron–phonon-induced interactions as in the conventional Bardeen–Cooper–Schrieffer theory1. A major challenge to the idea of magnetically mediated superconductivity has been the dramatically different behaviour of the cerium and ytterbium Heavy-Fermion compounds. The cerium-based Systems are often found to be superconducting1,2,3,4,5,6, in keeping with a magnetic pairing scenario, but corresponding ytterbium Systems, or hole analogues of the cerium Systems, are not. Despite searches over two decades there has been no evidence of Heavy-Fermion superconductivity in an ytterbium System, casting doubt on our understanding of the electron–hole parallelism between the cerium and the ytterbium compounds. Here we present the first empirical evidence that superconductivity is indeed possible in an ytterbium-based Heavy-Fermion System. In particular, we observe a superconducting transition at Tc=80 mK in high-purity single crystals of YbAlB4 in the new structural β phase7. We also observe a novel type of non-Fermi-liquid state above Tc that arises without chemical doping, in zero applied magnetic field and at ambient pressure, establishing β-YbAlB4 as a unique System showing quantum criticality without external tuning.

  • superconductivity and quantum criticality in the Heavy Fermion System beta ybalb4
    Nature Physics, 2008
    Co-Authors: Satoru Nakatsuji, Kentaro Kuga, Y Machida, Takashi Tayama, Toshiro Sakakibara, Yoshitomo Karaki, H Ishimoto, Shingo Yonezawa, Yoshiteru Maeno
    Abstract:

    A long-sought ytterbium-based Heavy-Fermion superconductor—a hole analogue of the cerium-based Systems—has been found. Moreover, there is evidence for a quantum critical point at ambient conditions and without chemical doping.