Joe David Thompson

We propose a predictive standard model for heavy electron systems based on a detailed phenomenological two-fluid description of existing experimental data. It leads to a new phase diagram that replaces the Doniach picture, describes the emergent anomalous scaling behavior of the heavy electron (Kondo) liquid measured below the lattice coherence temperature, T*, seen by many different experimental probes, that marks the onset of collective hybridization, and enables one to obtain important information on quantum criticality and the superconducting/antiferromagnetic states at low temperatures. Because T* is ~J^2\rho/2, the nearest neighbor RKKY interaction, a knowledge of the single-ion Kondo coupling, J, to the background conduction electron density of states, \rho, makes it possible to predict Kondo liquid behavior, and to estimate its maximum superconducting transition temperature in both existing and newly discovered heavy electron families.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) FAPEAM Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) U.S. DOE Made available in DSpace on 2014-11-13T21:35:54Z (GMT). No. of bitstreams: 1 WOS000281792400012.pdf: 969721 bytes, checksum: e6b5be1086931828c8bb6ef069e85dd8 (MD5) Previous issue date: 2010 Made available in DSpace on 2015-11-26T17:11:43Z (GMT). No. of bitstreams: 2 WOS000281792400012.pdf: 969721 bytes, checksum: e6b5be1086931828c8bb6ef069e85dd8 (MD5) WOS000281792400012.pdf.txt: 19809 bytes, checksum: 42bfd9d9ade300024d71730c5052ab12 (MD5) Previous issue date: 2010 We report a combined pressure-doping study in the nearly two-dimensional heavy fermion superconductor CeCoIn5 as its superconducting phase is driven to the normal state by Sn doping and/or applied pressure. Temperature-pressure-dependent electrical resistivity measurements were performed at the vicinity of a superconducting quantum critical point where T-c -> 0. A universal plot of the concentration- and pressure-dependent phase diagram suggests that for the concentrations studied a single mechanism is responsible for reducing T-c and bringing the system to the superconducting quantum critical point. A two-band model with hybridization controlled by pressure and doping provides a consistent description of the phase diagram and the suppression of the d-wave superconductivity in this material. 105 12 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) U.S. DOE Made available in DSpace on 2014-11-19T19:09:06Z (GMT). No. of bitstreams: 1 WOS000284046300010.pdf: 575788 bytes, checksum: 6302b1bdc88e578871c0d8a689df06ea (MD5) Previous issue date: 2010 Made available in DSpace on 2015-11-26T17:08:16Z (GMT). No. of bitstreams: 2 WOS000284046300010.pdf: 575788 bytes, checksum: 6302b1bdc88e578871c0d8a689df06ea (MD5) WOS000284046300010.pdf.txt: 34332 bytes, checksum: 894594df7cd0357b26a68b141079fd78 (MD5) Previous issue date: 2010 We report evidence of two superconducting phases in the Ce2Rh1-xIrxIn8 heavy fermion systems. One of these phases is pressure induced and occurs for a range of compositions situated near the Rh-rich extreme, consistent with the behavior observed for the pure Ce2RhIn8 compound. This superconducting region is expanded to higher critical temperatures and lower Rh concentrations with increasing pressure. It has a clear interplay with the established antiferromagnetic state, T-N similar to 2.8 K, suggesting that magnetic fluctuations are important for its realization. The second superconducting phase appears already at ambient pressure and it is characterized by a dome centered around x similar to 0.6 which, in sharp contrast with the first transition, is progressively eliminated by the application of pressure. These strikingly opposite behaviors under the same tuning parameter indicate the two transitions may have different natures. We compare these findings in the Ce2Rh1-xIrxIn8 alloys to its related CeRh1-xIrxIn5, arguing that the occurrence of the superconducting phases become unfavorable for the bilayers alloys due to higher dimensionality and stronger disorder. Further, we discuss whether the present results warrant similar claims with respect to the CeRh1-xIrxIn5 phase diagram and the possible nature of the superconducting phases. 82 18 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

We have studied the magnetic order inside the superconducting phase of CeCoIn5 for fields along the 1/2100 crystallographic direction using neutron diffraction. We find a spin density wave order with an incommensurate modulation Q 1/4 ðq; q; 1=2Þ and q 1/4 0:45ð1Þ which within our experimental uncertainty is indistinguishable from the spin density wave found for fields applied along 1/21 1 0. The magnetic order is thus modulated along the lines of nodes of the dx2 y2 superconducting order parameter suggesting that it is driven by the electron nesting along the superconducting line nodes. We postulate that the onset of magnetic order leads to reconstruction of the superconducting gap function and a magnetically induced pair density wave.

When subjected to pressure, the prototypical heavy-fermion antiferromagnet CeRhIn5 becomes superconducting, forming a broad dome of superconductivity centered around 2.35 GPa (=P2) with maximal Tc of 2.3 K. Above the superconducting dome, the normal state shows strange metallic behaviours, including a divergence in the specific heat and a sub-T-linear electrical resistivity. The discovery of a field-induced magnetic phase that coexists with superconductivity for a range of pressures P < P2 has been interpreted as evidence for a quantum phase transition, which could explain the non-Fermi liquid behavior observed in the normal state. Here we report electrical resistivity measurements of CeRhIn5 under magnetic field at P2, where the resistivity is sub-T-linear for temperatures above Tc (or T_FL) and a T^2-coefficient A found below T_FL diverges as Hc2 is approached. These results are similar to the field-induced quantum critical compound CeCoIn5 and confirm the presence of a quantum critical point in the pressure-induced superconductor CeRhIn5.

Made available in DSpace on 2014-11-14T05:57:52Z (GMT). No. of bitstreams: 1 WOS000243895600024.pdf: 214000 bytes, checksum: add75b5a5f4e26486ca180217f99e1c0 (MD5) Previous issue date: 2007 Made available in DSpace on 2015-11-26T16:04:39Z (GMT). No. of bitstreams: 2 WOS000243895600024.pdf: 214000 bytes, checksum: add75b5a5f4e26486ca180217f99e1c0 (MD5) WOS000243895600024.pdf.txt: 30622 bytes, checksum: dd83355012ec440a827a54b4cf4eec36 (MD5) Previous issue date: 2007 Electron spin resonance (ESR) results of Gd3+ in YbAl3 and LuAl3 are analyzed using a multiband (f-, d-, and p-type) model of correlated conduction electrons. The need for a multiband analysis of our results is based on the following observations: (i) the Korringa rates b similar or equal to 14 Oe/K and b similar or equal to 9 Oe/K for Gd3+ for YbAl3 and LuAl3, respectively, are larger than those expected from the respective measured g shifts (Knight shift), and (ii) negative and positive g shifts Delta g similar or equal to-0.004 and Delta g similar or equal to+0.003 were observed for Gd3+ in YbAl3 and LuAl3, respectively. Specific heat and magnetic susceptibility measurements, in the samples studied by ESR, show that electron-electron correlations are present in both compounds. 75 4