Point-contact study of the heavy-fermion superconductor CeCoIn5

Sumiyama, Akihiko; Onuki, R.; Oda, Yasukage; Shishido, Hiroaki; Settai, Rikio; Ōnuki, Yoshichika

doi:10.1016/j.jpcs.2008.06.036

Cited by 7 publications

(8 citation statements)

References 19 publications

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“…1c). However, measurements on all surfaces and on several samples reveal that this d-wave gap (with a magnitude of 535 ± 35 V, consistent with that extracted from point contact data 18,19 ) is filled (40%) with low energy excitations-a feature that cannot be explained by simple thermal broadening (determined to be 245 mK from measurements on a single-crystal Al sample, see supplementary section II). The complex multiband structure of CeCoIn 5 could involve different gaps on different Fermi surface sheets, and there is the possibility that some remain ungapped even at temperatures well below T c .…”

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Visualizing nodal heavy fermion superconductivity in CeCoIn5

et al. 2013

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Understanding the origin of superconductivity in strongly correlated electron systems continues to be at the forefront of the unsolved problems of physics 1 . Among the heavy f-electron systems, CeCoIn 5 is one of the most fascinating, as it shares many of the characteristics of correlated d-electron high-T c cuprate and pnictide superconductors 2-4 , including competition between antiferromagnetism and superconductivity 5 . Although there has been evidence for unconventional pairing in this compound 6-11 , high-resolution spectroscopic measurements of the superconducting state have been lacking. Previously, we have used high-resolution scanning tunnelling microscopy (STM) techniques to visualize the emergence of heavy fermion excitations in CeCoIn 5 and demonstrate the composite nature of these excitations well above T c (ref. 12). Here we extend these techniques to much lower temperatures to investigate how superconductivity develops within a strongly correlated band of composite excitations. We find the spectrum of heavy excitations to be strongly modified just before the onset of superconductivity by a suppression of the spectral weight near the Fermi energy (E F ), reminiscent of the pseudogap state 13,14 in the cuprates. By measuring the response of superconductivity to various perturbations, through both quasiparticle interference (QPI) and local pair-breaking experiments, we demonstrate the nodal d-wave character of superconducting pairing in CeCoIn 5 .CeCoIn 5 undergoes a superconducting transition at 2.3 K. Despite evidence of unconventional pairing, consensus on the mechanism of pairing and direct experimental verification of the order parameter symmetry are still lacking [6][7][8][9]11 . Moreover, experiments have suggested that superconductivity in this compound emerges from a state of unconventional quasiparticle excitations with a pseudogap phase similar to that found in underdoped high-T c cuprates [15][16][17] . Previously, we demonstrated that scanning tunnelling spectroscopic techniques can be used to directly visualize the emergence of heavy fermion excitations in CeCoIn 5 and their quantum critical nature 12 . Through these measurements, we also demonstrated the composite nature of heavy quasiparticles and showed their band formation as the f -electrons hybridize with the spd-electrons starting at 70 K, well above T c (ref. 12). This previous breakthrough, together with our recent development of high-resolution millikelvin STM, offers a unique opportunity to measure how superconductivity emerges in a heavy electron system. Figure 1 shows STM topographs of the two commonly observed atomically ordered surfaces of CeCoIn 5 produced after the cleaving of single crystals in situ in the ultra-high vacuum environment 1 Joseph Henry Laboratories and Department of Physics, Princeton University, Princeton, New Jersey 08544, USA, 2 Condensed Matter and Magnet Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA. † These authors contributed equally to this work. *e-mail: yazdani@pr...

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Visualizing nodal heavy fermion superconductivity in CeCoIn5

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“…A range of Á 0 values was suggested to result from the quality of the sample surface. 57) Indeed, recent STM investigations 24) showed the development of a pseudogap-like feature just above 5 K, but only on one type of surface (for the superconducting gap at lower temperature, Á SC % 0:6 meV was reported 23,24) ). Note that our data do not provide any indication for multiple order parameters.…”

Section: -5mentioning

confidence: 99%

Structural Investigations of CeIrIn₅ and CeCoIn₅ on Macroscopic and Atomic Length Scales

et al. 2014

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For any thorough investigation of complex physical properties, as encountered in strongly correlated electron systems, not only single crystals of highest quality but also a detailed knowledge of the structural properties of the material are pivotal prerequisites. Here, we combine physical and chemical investigations on the prototypical heavy fermion superconductors CeIrIn5 and CeCoIn5 on atomic and macroscopic length scale to gain insight into their precise structural properties. Our approach spans from enhanced resolution X-ray diffraction experiments to atomic resolution by means of Scanning Tunneling Microscopy (STM) and reveal a certain type of local features (coexistence of minority and majority structural patterns) in the tetragonal HoCoGa5-type structure of both compounds.

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“…The BCS estimate sets the scale, based on which the interaction regime of other superconducting systems are determined. Based on the point contact [113] and scanning tunnelling spectroscopy [114] used to de-termine the magnitude of the gap of any superconducting material, it has been observed that for CeCoIn 5 (α ∼ 5) 2∆ 0 /k B T c ∼ 7.73 [114], while for κ-BEDT (α ∼ 8) it is 2∆ 0 /k B T c ∼ 4.4 [115]. The iron superconductor is conjectured to be a two gap superconductor with the ratio for the smaller gap being 2∆ 0 /k B T c ∼ 1.4 and that of the larger gap being 2∆ 0 /k B T c ∼ 4.6 [116].…”

Section: Bcs-bec Crossover and Fflo Systemsmentioning

confidence: 99%

Imbalanced Fermi systems and exotic superconducting phases

Karmakar¹

2020

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Point-contact study of the heavy-fermion superconductor CeCoIn5

Cited by 7 publications

References 19 publications

Visualizing nodal heavy fermion superconductivity in CeCoIn5

Visualizing nodal heavy fermion superconductivity in CeCoIn5

Structural Investigations of CeIrIn₅ and CeCoIn₅ on Macroscopic and Atomic Length Scales

Imbalanced Fermi systems and exotic superconducting phases

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Point-contact study of the heavy-fermion superconductor CeCoIn5

Cited by 7 publications

References 19 publications

Visualizing nodal heavy fermion superconductivity in CeCoIn5

Visualizing nodal heavy fermion superconductivity in CeCoIn5

Structural Investigations of CeIrIn5 and CeCoIn5 on Macroscopic and Atomic Length Scales

Imbalanced Fermi systems and exotic superconducting phases

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Product

Resources

About

Structural Investigations of CeIrIn₅ and CeCoIn₅ on Macroscopic and Atomic Length Scales