Electronic properties and phase transitions of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">RbC</mml:mi></mml:mrow><mml:mrow><mml:mn>60</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">CsC</mml:mi></mml:mrow><mml:mrow><mml:mn>60</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>: In

Tycko, Robert; Dabbagh, G.; Murphy, D. W.; Zhu, Qian; Fischer, J. E.

doi:10.1103/physrevb.48.9097

Cited by 118 publications

(79 citation statements)

References 43 publications

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“…Upon heating, treatment (B), the specimen exhibits a phase transition around 120 o C. The temperature hysteresis suggests that the transition is of first order. As confirmed by our X-ray data, this is the structural transition observed by Zhu et al [8], although the transition temperature seems to be sample dependent (120 o C [8,4], 140 o C [6], 70 o C [7], and 90 o C [14]). The detailed evaluation of these transmission data indicate that the material is an electrical conductor.…”

supporting

confidence: 88%

“…Earlier X-ray studies on the x = 1 compound by Zhu et al [8] established the existence of a rocksalt structure at high temperature, with a phase transition at around 120 o C. Jànossy et al tentatively assigned the narrower CESR signal to the x = 1 material, and argued that it is a metal at high temperatures. On the other hand, Tycko et al [7] interpreted NMR results on RbC 60 in terms of a paramagnetic insulator. We set out to explore this compound by utilizing the direct link between IR transmission and conductivity.…”

mentioning

confidence: 99%

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Insulating and conducting phases ofRbC60

Martin

Koller

et al. 1994

Phys. Rev. B

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Optical measurements were performed on thin films of RbxC60, identified by X-ray diffraction as mostly x = 1 material. The samples were subjected to various heat treatments, including quenching and slow cooling from 400K. The dramatic increase in the transmission of the quenched samples, and the relaxation towards the transmission observed in slow cooled samples provides direct evidence for the existence of a metastable insulating phase. Slow cooling results in a phase transition between two electrically conducting phases.

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supporting

confidence: 88%

mentioning

confidence: 99%

Insulating and conducting phases ofRbC60

Martin

Koller

et al. 1994

Phys. Rev. B

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“…These materials were identified from a Raman analysis of the potassium compound. From X-ray structural investigations the compound was found to have an fcc lattice with a rocksalt structure, where the potassium ions are located on the octahedral interstitial lattice sites [115,116].…”

Section: (3b) Alkali Metal Doped Fullerenesmentioning

confidence: 99%

Solid State and Magnetic Properties of Pure, Intercalated and Superconducting Fullerenes

Buntar¹,

Sauerzopf²,

Weber³

1997

Aust. J. Phys.

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A review of some of the solid state and the magnetic properties of fullerenes is presented. We summarise and discuss experimental results on magnetism of pure C60, C70 and higher fullerenes. The main features of the structure and the magnetic properties of intercalated fullerenes, such as metallofullerenes, TDAE-C60 and polymeric A1C60, are presented. Attention is also paid to the mixed state properties of fullerene superconductors, especially to the evaluation of the critical fields and the characteristic lengths of these materials. Some new experimental results on this subject are also presented.

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“…As we have indicated in the introduction, these compounds do however display a complicated phase diagram, as a structural transition toward a polymer phase occurs below 300K, so that the fcc phase could initially only be studied at the highest temperatures. Cs NMR shift [26] and the ESR signal intensity [27] both display a Curie type variation, as shown by the full line fit [28]. Hence the disordered arrows on the C 60 balls, which sketch the S=1/2 Mott insulating state.…”

Section: A 1 C 60 Compounds: Local Singletsmentioning

confidence: 80%

“…There, both NMR [26] and ESR studies [27] indicate that the spin susceptibility displays a Curie law, with an effective moment which corresponds to a spin S=1/2 and a very weak extrapolated Weiss temperature [28], as can be seen in figure 4. Such a Mott insulating state is somewhat expected and indicates that the electrons donated by Cs are localized on the C 60 .…”

Section: A 1 C 60 Compounds: Local Singletsmentioning

confidence: 99%

Electronic Correlations, Jahn-Teller Distortions and Mott Transition to Superconductivity in Alkali-C₆₀Compounds

Alloul

2012

EPJ Web of Conferences

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Abstract. The discovery in 1991 of high temperature superconductivity (SC) in A 3 C 60 compounds, where A is an alkali ion, has been rapidly ascribed to a BCS mechanism, in which the pairing is mediated by on ball optical phonon modes. While this has lead to consider that electronic correlations were not important in these compounds, further studies of various A n C 60 with n=1, 2, 4 allowed to evidence that their electronic properties cannot be explained by a simple progressive band filling of the C 60 six-fold degenerate t 1u molecular level. This could only be ascribed to the simultaneous influence of electron correlations and Jahn-Teller Distortions (JTD) of the C 60 ball, which energetically favour evenly charged C 60 molecules. This is underlined by the recent discovery of two expanded fulleride Cs 3 C 60 isomeric phases which are Mott insulators at ambient pressure. Both phases undergo a pressure induced first order Mott transition to SC with a (p, T) phase diagram displaying a dome shaped SC, a common situation encountered nowadays in correlated electron systems. NMR experiments allowed us to study the magnetic properties of the Mott phases and to evidence clear deviations from BCS expectations near the Mott transition. So, although SC involves an electron-phonon mechanism, the incidence of electron correlations has an importance on the electronic properties, as had been anticipated from DMFT calculations.

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Electronic properties and phase transitions ofRbC60andCsC60: In

Cited by 118 publications

References 43 publications

Insulating and conducting phases ofRbC60

Insulating and conducting phases ofRbC60

Solid State and Magnetic Properties of Pure, Intercalated and Superconducting Fullerenes

Electronic Correlations, Jahn-Teller Distortions and Mott Transition to Superconductivity in Alkali-C₆₀Compounds

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Electronic properties and phase transitions ofRbC60andCsC60: In

Cited by 118 publications

References 43 publications

Insulating and conducting phases ofRbC60

Insulating and conducting phases ofRbC60

Solid State and Magnetic Properties of Pure, Intercalated and Superconducting Fullerenes

Electronic Correlations, Jahn-Teller Distortions and Mott Transition to Superconductivity in Alkali-C60Compounds

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Electronic Correlations, Jahn-Teller Distortions and Mott Transition to Superconductivity in Alkali-C₆₀Compounds