Isotropic quantum scattering and unconventional superconductivity

Park, Tuson; Sidorov, V. A.; Ronning, F.; Zhu, Jian‐Xin; Tokiwa, Y.; Lee, H.; Bauer, E. D.; Movshovich, R.; Sarrao, J. L.; Thompson, J. D.

doi:10.1038/nature07431

Cited by 117 publications

(169 citation statements)

References 24 publications

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“…This, like its antiferromagnetic counterpart (2,37,38), in turn raises the possibility of a new type of superconductivity; the underlying quantum fluctuations would be associated with not only the development of the ferromagnetic order (12) but also the transformation of a large-to-small Fermi surface. Theoretically, accessing the quantum phase transition requires that our analysis be extended to the regime where the Kondo coupling is large compared to the RKKY interaction, and this represents an important direction for the future.…”

Section: Discussionmentioning

confidence: 99%

Metallic ferromagnetism in the Kondo lattice

Yamamoto

2010

Proc. Natl. Acad. Sci. U.S.A.

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Metallic magnetism is both ancient and modern, occurring in such familiar settings as the lodestone in compass needles and the hard drive in computers. Surprisingly, a rigorous theoretical basis for metallic ferromagnetism is still largely missing. The Stoner approach perturbatively treats Coulomb interactions when the latter need to be large, whereas the Nagaoka approach incorporates thermodynamically negligible holes into a half-filled band. Here, we show that the ferromagnetic order of the Kondo lattice is amenable to an asymptotically exact analysis over a range of interaction parameters. In this ferromagnetic phase, the conduction electrons and local moments are strongly coupled but the Fermi surface does not enclose the latter (i.e., it is "small"). Moreover, non-Fermi-liquid behavior appears over a range of frequencies and temperatures. Our results provide the basis to understand some long-standing puzzles in the ferromagnetic heavy fermion metals, and raise the prospect for a new class of ferromagnetic quantum phase transitions. Fermi surface | itinerant magnetism | non-Fermi liquidA contemporary theme in quantum condensed matter physics concerns competing ground states and the accompanying novel excitations (1). With a plethora of different phases, magnetic heavy fermion materials should reign supreme as the prototype for competing order. So far, most of the theoretical scrutiny has focused on antiferromagnetic heavy fermions (2, 3). Nonetheless, the list of heavy fermion metals that are known to exhibit ferromagnetic order continues to grow. An early example subjected to extensive studies is CeRu 2 Ge 2 (ref. 4 and references therein). Other ferromagnetic heavy fermion metals include CePt (5), CeSi x (6), CeAgSb 2 (7), and URu 2−x Re x Si 2 at x > 0.15 (8, 9). More recently discovered materials include CeRuPO (10) and UIr 2 Zn 20 (11). Finally, systems such as UGe 2 (12) and URhGe (13) are particularly interesting because they exhibit a superconducting dome as their metallic ferromagnetism is tuned toward its border. Some fascinating and general questions have emerged (14,15,16), yet they have hardly been addressed theoretically. One central issue concerns the nature of the Fermi surface: Is it "large," encompassing both the local moments and conduction electrons as in paramagnetic heavy fermion metals (17, 18), or is it "small," incorporating only conduction electrons? Measurements of the de Haas-van Alphen (dHvA) effect have suggested that the Fermi surface is small in CeRu 2 Ge 2 (14-16), and have provided evidence for Fermi surface reconstruction as a function of pressure in UGe 2 (19,20). At the same time, it is traditional to consider the heavy fermion ferromagnets as having a large Fermi surface when their relationship with unconventional superconductivity is discussed (12,13,21); an alternative form of the Fermi surface in the ordered state could give rise to a new type of superconductivity near its phase boundary. All these point to the importance of theoretically understanding the ferromagnet...

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Section: Discussionmentioning

confidence: 99%

Metallic ferromagnetism in the Kondo lattice

Yamamoto

2010

Proc. Natl. Acad. Sci. U.S.A.

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“…The latter scenario is also assumed in CeRhIn 5 , mainly based on the subsistence of SC in a wide region around p c , the maximum in ρ 0 , and a T -linear resistivity (n ∼ 1). [32][33][34] Using our method could be an important ingredient for probing the existence of a CEP and the relevancy of VF, notably for SC, in these compounds. Nonetheless, another dissimilarity to CeCu 2 Si 2 may occur: The resistance drop associated with the delocalization may be less pronounced, which means experimentally less accessible, due to a lower lying CEP (more negative T cr ).…”

Section: General Relevancy Of ρ( P) Analysismentioning

confidence: 99%

Heavy fermion superconductor CeCu2Si2under high pressure: Multiprobing the valence crossover

Seyfarth

Rüetschi²,

Sengupta³

et al. 2012

Phys. Rev. B

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The first heavy fermion superconductor CeCu 2 Si 2 has not revealed all its striking mysteries yet. At high pressures, superconductivity is supposed to be mediated by valence fluctuations, in contrast to ambient pressure, where spin fluctuations most likely act as pairing glue. We have carried out a multiprobe (electric transport, thermopower, ac specific heat, Hall and Nernst effects) experiment up to 7 GPa on a high-quality CeCu 2 Si 2 single crystal. For the first time, the resistivity data make it possible quantitatively to draw the valence crossover line within the p-T plane and to locate the critical end point at 4.5 ± 0.2 GPa and a slightly negative temperature. In the same pressure region, remarkable features have also been detected in the other physical properties, presumably acting as further signatures of the Ce valence crossover and the associated critical fluctuations: We observe maxima in the Hall and Nernst effects and a sign change and a strong sensitivity on magnetic field in the thermopower signal.

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“…At 1.38 GPa, the pressure where T c is a maximum at zero magnetic field, r c (T) deviates from a T 2 dependence, following a sub-T linear dependence over an extended temperature range from the base temperature ( ¼ 0.3 K) to 7 K, that is, r c ¼ r 0 þ AT n with n ¼ 0.69 and r 0 ¼ 78.5 mO cm. We note that the fitting parameters are n ¼ 0.71 and r 0 ¼ 5.2 mO cm for pure CeRhIn 5 at 2.35 GPa, the QCP, as well as the optimal pressure for superconductivity 16 .…”

Section: Qcp Andmentioning

confidence: 99%

Controlling superconductivity by tunable quantum critical points

et al. 2015

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The heavy fermion compound CeRhIn 5 is a rare example where a quantum critical point, hidden by a dome of superconductivity, has been explicitly revealed and found to have a local nature. The lack of additional examples of local types of quantum critical points associated with superconductivity, however, has made it difficult to unravel the role of quantum fluctuations in forming Cooper pairs. Here, we show the precise control of superconductivity by tunable quantum critical points in CeRhIn 5 . Slight tin-substitution for indium in CeRhIn 5 shifts its antiferromagnetic quantum critical point from 2.3 GPa to 1.3 GPa and induces a residual impurity scattering 300 times larger than that of pure CeRhIn 5 , which should be sufficient to preclude superconductivity. Nevertheless, superconductivity occurs at the quantum critical point of the tin-doped metal. These results underline that fluctuations from the antiferromagnetic quantum criticality promote unconventional superconductivity in CeRhIn 5 .

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Isotropic quantum scattering and unconventional superconductivity

Cited by 117 publications

References 24 publications

Metallic ferromagnetism in the Kondo lattice

Metallic ferromagnetism in the Kondo lattice

Heavy fermion superconductor CeCu2Si2under high pressure: Multiprobing the valence crossover

Controlling superconductivity by tunable quantum critical points

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