Neutron diffraction and micro-Raman scattering studies on rare-earth carbide halides

Henn, R.; Strach, T.; Kremer, Reinhard K.; Simon, Arndt

doi:10.1103/physrevb.58.14364

Cited by 18 publications

(14 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The C-C stretch of the C 2 dimer has the highest frequency. These are consistent with the previous experimental characterization of the Raman-active modes 62 and first-principles simulation. 23 Note that the appearance of the dimer rigid-body vibrations at intermediate-frequency regimes is a feature common to YC 2 (Ref.…”

Section: Phononic Propertiessupporting

confidence: 92%

See 1 more Smart Citation

Chemical physics of superconductivity in layered yttrium carbide halides from first principles

Akashi,

Arita,

Zhang

et al. 2021

Preprint

View full text Add to dashboard Cite

We perform a thorough first-principles study on superconductivity in yttrium carbide halide Y2X2C2 (X=Cl, Br, I) whose maximum transition temperature (Tc) amounts to ∼10 K. A detailed analysis on the optimized crystal structures reveals that the Y2C2 blocks are compressed uniaxially upon the halogen substitution from Cl, Br to I, contrary to the monotonic expansion of the lattice vectors. With a nonempirical method based on the density functional theory for superconductors within the conventional phonon mechanism, we successfully reproduce the halogen dependence of Tc. Anomalously enhanced coupling of one C2 libration mode is observed in Y2I2C2, which imply possible departure from the conventional pairing picture. Utilizing the Wannier representation of the electron-phonon coupling, we show that the halogen electronic orbitals and ionic vibrations scarcely contribute to the superconducting pairing. The halogen dependence of this system is hence an indirect effect of the halogen ions through the uniaxial compressive force on the superconducting Y2C2 blocks. We thus establish a quantitatively reliable picture of the superconducting physics of this system, extracting a unique effect of the atomic substitution which is potentially applicable to other superconductors.

show abstract

Section: Phononic Propertiessupporting

confidence: 92%

“…This perspective has apparently been obscured by the expansion of the lattice vectors. It is hence encouraged to revisit the experimental 16,62 and previous firstprinciples 23 data to see if this Poisson-type structural change of the yttrium framework is indeed presented.…”

Section: A Structural Propertiesmentioning

confidence: 99%

Chemical physics of superconductivity in layered yttrium carbide halides from first principles

Akashi,

Arita,

Zhang

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…The substitution experiments allow one to attribute an energy range below 300 cm À1 to such phonons involving rare-earth and/or halogen atom vibrations exclusively [15]. Additionally, considerably broader modes are observed at % 400 and % 1600 cm À1 (Fig.…”

Section: Resultsmentioning

confidence: 95%

“…Neutron diffraction studies have revealed a shortening of the C±C bond length as compared to the bond length found for typical C±C double-bonds, e.g. in organic compounds [13,15]. In a preceeding Raman scattering study we have investigated the phonon spectrum of some RE 2 C 2 X 2 phases and identified the vibrations of the heavy atom and carbon atom sublattices [15].…”

Section: Introductionmentioning

confidence: 98%

“…in organic compounds [13,15]. In a preceeding Raman scattering study we have investigated the phonon spectrum of some RE 2 C 2 X 2 phases and identified the vibrations of the heavy atom and carbon atom sublattices [15]. Here we present a more detailed comparison of the carbon based vibrations in Y 2 C 2 X 2 (X = Br, I) and in Y 2 C 2 Br 0X5 I 1X5 , the compound with the highest T c in the yttrium based phases.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Raman Scattering Studies of the Carbon Atom Vibrations in Superconducting Rare-Earth Carbide Halides RE2C2(X,X?)2 (RE = Y, Gd; X, X? = Br, I)

Henn

Strach

Kremer

et al. 1999

phys. stat. sol. (b)

Self Cite

View full text Add to dashboard Cite

Carbon Based Superconductors

Kremer

Kim

Simon

2007

High Tc Superconductors and Related Transition Metal Oxides

Self Cite

View full text Add to dashboard Cite

We review the characteristics of some carbon based novel superconductors which emerged in the past two decades since the discovery of superconductivity in the high-T c oxocuprates. In particular, we summarize the properties of ternary layered carbide halides of the rare rarth metals with composition RE 2 C 2 X 2 (RE = Y, La; X=Cl, Br, I) and of the rare earth di-and sesquicarbides, YC 2 , LaC 2 and La 2 C 3 . Finally, we briefly discuss the properties of the recently discovered Ca and Yb intercalated graphite superconductors, CaC 6 and YbC 6 . PACS numbers: abc 1 I. INTRODUCTIONThe discovery of high-T c superconductivity by Bednorz and Müller 1 in 1986 marks the beginning of a period of a vivid search for -chemically and physically partly extremely complex -new oxocuprates and for theoretical approaches to understand their puzzling properties, quite a few of which remained controversial even until today. The advent of this completely unexpected class of new superconductors also revived the interest in more conventional -'low-T c ' -superconductors. In due course, a number of new systems were found, and already known superconductors were reinvestigated with improved and refined experimental and theoretical tools. These activities led to surprising new discoveries as that of the 40 K superconductor MgB 2 by Nagamatsu et al. 2 Apart from its T c , MgB 2 is special primarily for two reasons: Compared e.g. to the high-T c oxocuprates its crystal structure is of remarkable simplicity allowing electronic and phononic structure calculations of high precision, and MgB 2 is the first system for which multigap superconductivity has independently been evidenced by several experimental techniques. 3,4,5 Until the discovery of MgB 2 , doped fullerenes had shown the highest T c values after the high-T c oxocuprates. With large enough quantities of purified C 60 available, 6 Hebard et al. prepared superconductors with a T c of 18 K by doping polycrystalline C 60 and C 60 films with alkali metals. 7 Subsequently, by adjusting the separation of the C 60 molecules using a proper composition of different alkali metals, T c 's up to ∼33 K were reached. 8 Superconductivity in doped fullerenes also redraw attention to carbon based superconductors in general. Especially, binary and quasibinary transition metal carbides have a long history in showing T c 's which were among the highest found before the discovery of the high-T c oxocuprates. 9 Later borocarbides of composition REM 2 B 2 C, with RE = Y or Lu and M = Ni or Pd, with T c 's up to 22 K attracted considerable interest. 10,11 Superconductivity in graphite intercalation compounds (GICs) is another early field of research which recently was revived. The discovery of superconducting GICs dates back to the pioneering work of Bernd Matthias' group in the 1960's, however, the T c 's of these early GICs remained well below 1 K. 12,13 Subsequently, the T c 's of alkali metal intercalated GICs could be raised by intercalation under pressure with e.g. Li and Na, but T c did not signifi...

show abstract

Neutron diffraction and micro-Raman scattering studies on rare-earth carbide halides

Cited by 18 publications

References 24 publications

Chemical physics of superconductivity in layered yttrium carbide halides from first principles

Chemical physics of superconductivity in layered yttrium carbide halides from first principles

Raman Scattering Studies of the Carbon Atom Vibrations in Superconducting Rare-Earth Carbide Halides RE2C2(X,X?)2 (RE = Y, Gd; X, X? = Br, I)

Carbon Based Superconductors

Contact Info

Product

Resources

About