Recent Advances in Ce-Based Heavy-Fermion Superconductivity and Fermi Surface Properties

Settai, Rikio; Takeuchi, Tetsuya; Ōnuki, Yoshichika

doi:10.1143/jpsj.76.051003

Cited by 158 publications

(144 citation statements)

References 117 publications

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“…Ce compounds reveal characteristic properties such as magnetic orderings, heavy fermion, and unconventional superconductivity [1]. These are based on a competitive phenomenon between the RKKY interaction and Kondo effect.…”

Section: Introductionmentioning

confidence: 99%

Drastic Change of Electronic Properties in Ce₂MgSi₂ and CeNiIn₄ under High Pressure

Honda¹,

Yoshitani²,

Hirose³

et al. 2014

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013)

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For an antiferromagnetic Ce 2 MgSi 2 single crystal sample, we measured the electrical resistivity under high pressure, and observed a remarkable phenomenon in the quantum critical region where the Néel temperature becomes zero. The corresponding critical pressure P c is 6 GPa. The electrical resistivity in the quantum critical region is found to increase steeply in magnitude with decreasing temperature, following the −log T dependence, and reaches a huge residual resistivity at low temperatures. Note that the corresponding resistivity is unchanged below about 1 K and does not decrease at lower temperatures. This behavior is very similar to the impurity Kondo effect, although Ce 2 MgSi 2 belongs to the Kondo lattice system. At pressures larger than P c 6 GPa in Ce 2 MgSi 2 , the residual resistivity becomes small, and the electronic state is changed into the so-called valence fluctuating system with a large Kondo temperature. The similar result is observed in another antiferromagnet CeNiIn 4 , revealing a huge residual resistivity and no decrease of the low-temperature resistivity at 16.2 and 18.1 GPa.

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Section: Introductionmentioning

confidence: 99%

Drastic Change of Electronic Properties in Ce₂MgSi₂ and CeNiIn₄ under High Pressure

Honda¹,

Yoshitani²,

Hirose³

et al. 2014

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2013)

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“…Despite its layered structure, the largely corrugated Fermi surface 13 , 3D-like antiferromagnetic fluctuations in the normal state 14 , and small anisotropy of upper critical field 15 , all indicate that the electronic, magnetic and superconducting properties are essentially 3D rather than 2D. Therefore it is still unclear to which extent the 3D nature is essential for the superconductivity of CeCoIn 5 .…”

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Extremely strong-coupling superconductivity in artificial two-dimensional Kondo lattices

et al. 2011

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When interacting electrons are confined to low-dimensions, the electron-electron correlation effect is enhanced dramatically, which often drives the system into exhibiting behaviours that are otherwise highly improbable. Superconductivity with the strongest electron correlations is achieved in heavy-fermion compounds, which contain a dense lattice of localized magnetic moments interacting with a sea of conduction electrons to form a three-dimensional (3D) Kondo lattice 1 . It had remained an unanswered question whether superconductivity would persist upon effectively reducing the dimensionality of these materials from three to two. Here we report on the observation of superconductivity in such an ultimately strongly-correlated system of heavy electrons confined within a 2D square-lattice of Ce-atoms (2D Kondo lattice), which was realized by fabricating epitaxial superlattices 2,3 built of alternating layers of heavy-fermion CeCoIn 5 4 and conventional metal YbCoIn 5 . The field-temperature phase diagram of the superlattices exhibits highly unusual behaviours, including a striking enhancement of the upper critical field relative to the transition temperature. This implies that the force holding together the superconducting electron-pairs takes on an extremely strong coupled nature as a result of two-dimensionalisation. The layered heavy-fermion compound CeCoIn 5 has the highest superconducting transition temperature (T c =2.3 K) among rare-earth-based heavy-fermion materials 4 . Its electronic properties are characterized by anomalously large value of the linear contribution to the specific heat (Sommerfeld coefficient ~1 J/mol K 2 ) indicating heavy effective masses of the 4f electrons which contribute greatly to the Fermi surface. The tetragonal CeCoIn 5 crystal structure is built from alternating layers of CeIn 3 and CoIn 2 stacked along the [001] direction. This compound possesses several key features for understanding the unconventional superconductivity in strongly correlated systems [5][6][7] . The superconductivity with d x 2 -y 2 pairing symmetry 8-11 which occurs in the proximity of a magnetic instability is a manifestation of magnetic fluctuations mediated superconductivity [5][6][7]12 .A very strong coupling superconductivity, where electron-pairs are bound together by strong forces, is revealed by a large specific heat jump 4 at T c representing a steep drop of the entropy below T c , and a large superconducting energy gap  needed to break the electron-pair , all indicate that the electronic, magnetic and superconducting properties are essentially 3D rather than 2D. Therefore it is still unclear to which extent the 3D nature is essential for the superconductivity of CeCoIn 5 .Recently the state-of-the-art technique has been developed to reduce the dimensionality of the heavy electrons in a controllable fashion by the layer-by-layer epitaxial growth of Ce-based materials. Previously a series of antiferromagnetic superlattices CeIn 3 /LaIn 3 have been successfully grown 2 , but it remains open whethe...

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“…An important difference between the two systems is that SC in CeIn 3 occurs only in a very narrow pressure regime and below 0.2 K, whereas T c values above 2 K are observed in CeRhIn 5 between 2 and 4 GPa. Although the low-T electrical resistivity of CeIn 3 has shown an anomalous exponent of 1.6 [10], nuclear quadrupole resonance suggests a Landau Fermi liquid ground state [18], and the cyclotron mass derived from dHvA experiments is constant near the discontinuous QPT [21]. For CeRhIn 5 the cyclotron mass m ⋆ (p) [21] and the coefficient A(p) of T 2 behavior in the electrical resistivity at 15 T [20] show diverging behavior, suggesting a field-induced QCP close to p c ≈ 2.5 GPa.…”

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Quantum criticality in layered \chem{{CeRhIn}_{5-{x}}Sn_{x}} compared with cubic \chem{{CeIn}_{3-{x}}Sn_{x}}

et al. 2009

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Abstract. -We report low-temperature thermal-expansion measurements on single crystals of the layered heavy fermion system CeRhIn5−xSnx (0.3 ≤ x ≤ 0.6) and compare it with a previous study on the related cubic system CeIn3−xSnx [R. Küchler et al., Phys. Rev. Lett. 96, 256403 (2006)]. Both systems display a quantum critical point as proven by a divergent Grüneisen ratio. Most remarkably, the three-dimensional itinerant model explains quantum criticality in both systems, suggesting that the crystalline anisotropy in CeRhIn5−xSnx is unimportant. This is ascribed to the effect of weak disorder in these doped systems.Quantum critical points (QCPs) in intermetallic compounds are of great scientific interest, as they provide the origin of non-Fermi liquid (NFL) behavior and novel ground states like unconventional superconductivity (SC). Heavy fermion (HF) systems, i.e. rare-earth or actinidebased compounds with competing Kondo-and exchange interactions are prototype systems for the investigation of QCPs, and different classes of QCPs have been identified [1]. In one class, the observed properties are in agreement with the predictions of the spin-density-wave (SDW) theory, which considers the f -electrons as itinerant in the entire regime close to the QCP. In another class of materials (most prominent examples include CeCu 6−x Au x [2] and YbRh 2 Si 2 [3-5]) there are strong indications for a localization-transition of the f -electrons due to the breakdown of Kondo screening at the QCP. SC has been observed in some but not all compounds close to QCPs and may even occur near first-order quantum phase transitions (QPTs) like in CeRh 2 Si 2 [6, 7] under pressure, which lack any signatures of NFL behavior.There are several indications that magnetic anisotropy may be a crucial parameter for quantum criticality: (i) quasi-two-dimensional (2D) magnetic fluctuations have been observed at the QCP in orthorhombic CeCu 5.9 Au 0.1 [8] with an anomalous energy over temperature scaling of the dynamical susceptibility [2], which strongly violates the predictions of the itinerant SDW theory, (ii) a locally critical QCP has been predicted for the case of 2D magnetic fluctuations [9], (iii) SC in layered CeTIn 5 (T=Co, Ir, Rh) occurs at ten times higher temperatures compared to the cubic relative CeIn 3 [10,11] and (iv) spin-liquid formation among the local moments, proposed in the presence of strong geometrical frustration (which may possibly be enhanced in 2D magnetic systems), may act as competing mechanism against the Kondo-singlet formation [12,13].In order to systematically investigate the relevance of magnetic anisotropy on quantum criticality, a comparison of cubic CeIn 3 with layered CeTIn 5 is most promising. The cubic point symmetry of Ce atoms in the former must lead to isotropic magnetic fluctuations. By contrast, in CeTIn 5 the alternating series of CeIn 3 and TIn 2 , stacked along the c-axis (for the crystal structures see Fig. 1 Hydrostatic pressure experiments have been performed on cubic CeIn 3 (Néel temperature T N at ...

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Recent Advances in Ce-Based Heavy-Fermion Superconductivity and Fermi Surface Properties

Cited by 158 publications

References 117 publications

Drastic Change of Electronic Properties in Ce₂MgSi₂ and CeNiIn₄ under High Pressure

Drastic Change of Electronic Properties in Ce₂MgSi₂ and CeNiIn₄ under High Pressure

Extremely strong-coupling superconductivity in artificial two-dimensional Kondo lattices

Quantum criticality in layered \chem{{CeRhIn}_{5-{x}}Sn_{x}} compared with cubic \chem{{CeIn}_{3-{x}}Sn_{x}}

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Recent Advances in Ce-Based Heavy-Fermion Superconductivity and Fermi Surface Properties

Cited by 158 publications

References 117 publications

Drastic Change of Electronic Properties in Ce2MgSi2 and CeNiIn4 under High Pressure

Drastic Change of Electronic Properties in Ce2MgSi2 and CeNiIn4 under High Pressure

Extremely strong-coupling superconductivity in artificial two-dimensional Kondo lattices

Quantum criticality in layered \chem{{CeRhIn}_{5-{x}}Sn_{x}} compared with cubic \chem{{CeIn}_{3-{x}}Sn_{x}}

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Drastic Change of Electronic Properties in Ce₂MgSi₂ and CeNiIn₄ under High Pressure

Drastic Change of Electronic Properties in Ce₂MgSi₂ and CeNiIn₄ under High Pressure