Superconductivity under high pressure in the binary compound<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>CaLi</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>

Debessai, M.; Matsuoka, Toshifumi; Hamlin, J. J.; Gangopadhyay, A. K.; Schilling, J. S.; Shimizu, Katsuya; Ohishi, Yasuo

doi:10.1103/physrevb.78.214517

Cited by 30 publications

(53 citation statements)

References 34 publications

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“…Indeed, Eu was found to be superconducting above 80 GPa with a critical temperature T c ≈ 2 K [11]. However, both T c and its small positive pressure derivative dT c /dP to 142 GPa lie well below the values found in the nonmagnetic trivalent spd-electron metals Sc, Y, La, and Lu [24]. Possible explanations include that the persistence of magnetic order in Eu suppresses T c or that Eu does not become fully trivalent to 142 GPa.…”

Section: Introductionmentioning

confidence: 95%

Magnetism of europium under extreme pressures

Lim

Fabbris

et al. 2016

Phys. Rev. B

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Using synchrotron-based Mössbauer and x-ray emission spectroscopies, we explore the evolution of magnetism in elemental (divalent) europium as it gives way to superconductivity at extreme pressures. Magnetic order in Eu is observed to collapse just above 80 GPa as superconductivity emerges, even though Eu cations retain their strong local 4f 7 magnetic moments up to 119 GPa with no evidence for an increase in valence.We speculate that superconductivity in Eu may be unconventional and have its origin in magnetic fluctuations, as has been suggested for high-T c cuprates, heavy fermions and iron-pnictides.

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Section: Introductionmentioning

confidence: 95%

Magnetism of europium under extreme pressures

Lim

Fabbris

et al. 2016

Phys. Rev. B

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“…16 Scandium, with one more (3d) electron than Ca, undergoes phase transitions from hcp to Sc-II at 20 GPa and to a Sc-III phase at 107 GPa. 20,21 Although Sc is conventionally grouped together with Y and the lanthanide metals as the rare-earth metals, due to their similarities in their outer electron configurations, its structural transition sequence is rather different from the common sequence of lanthanide metals and Y, which follow the pattern hcp→ Smtype→ dhcp→ fcc→ distorted fcc. The Sc-II structure is complex, and was recently found to be best fitted to a pseudo bcc structure with 24 atoms in the unit cell.…”

Section: Comparison To Related Metalsmentioning

confidence: 99%

“…Its T c drops dramatically to 8 K at the phase transition from Sc-II to Sc-III around 107 GPa. 21 Considering the close relation of Sc and Sr to Ca in the periodic table and the similar superconducting properties under pressure, it could be expected that Ca under pressure should have more complex structures, rather than the observed sc structure. In fact, Olijnyk and Holzapfel 10 observed that their Ca sample transformed from sc to an unidentified complex structure at 42 GPa.…”

Section: Comparison To Related Metalsmentioning

confidence: 99%

Competing phases, strong electron-phonon interaction, and superconductivity in elemental calcium under high pressure

Gygi

Pickett

2009

Phys. Rev. B

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The observed "simple cubic" (sc) phase of elemental Ca at room temperature in the 32-109 GPa range is, from linear response calculations, dynamically unstable. By comparing first principle calculations of the enthalpy for five sc-related (non-close-packed) structures, we find that all five structures compete energetically at room temperature in the 40-90 GPa range, and three do so in the 100-130 GPa range. Some competing structures below 90 GPa are dynamically stable, i.e., no imaginary frequency, suggesting that these sc-derived short-range-order local structures exist locally and can account for the observed (average) "sc" diffraction pattern. In the dynamically stable phases below 90 GPa, some low frequency phonon modes are present, contributing to strong electron-phonon (EP) coupling as well as arising from the strong coupling. Linear response calculations for two of the structures over 120 GPa lead to critical temperatures in the 20-25 K range as is observed, and do so without unusually soft modes.

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“…If this transition did not occur, Sc would exhibit a T c higher than 20 K. In simple-metal superconductors such as Al, Sn, and Pb, T c decreases with increasing pressure due to a decrease of the electronic density of states (DOS). The pressure effects on T c in Ca and Sc, opposite to those in simple metals, have been discussed in terms of the pressure-induced s−d electron transfer where 4s electrons are dominant for electron conduction at ambient pressure and are transferred to the narrower 3d band by applying pressure [4,5]. The electrons occupying the 3d band play an important role in relatively high T c superconductivity.…”

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confidence: 99%

“…T c increases with increasing pressure and exceeds 20 K at ~100 GPa [2], which is the highest T c in all elemental metals. Sc exhibits a superconducting transition above ~60 GPa, which approaches 20 K at 107 GPa [3,4]. At higher pressures, however, Sc undergoes a structural phase transition to a nonsuperconducting phase (Sc-III).…”

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Superconductivity in the Hexagonal Ternary Phosphide ScIrP

et al. 2016

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We report the discovery of a bulk superconducting transition at 3.4 K in the ternary phosphide, ScIrP, which crystallizes in a hexagonal ZrNiAl-type structure without spatial inversion symmetry. On the basis of heat capacity data in a zero magnetic field, ScIrP is suggested to be a weakly-coupled Bardeen-Cooper-Schrieffer superconductor. Alternatively, experimental results under magnetic fields indicate that this material is a type-II superconductor with an upper critical field H c2 at magnetic fields above 5 T at zero temperature. This moderately high H c2 does not violate the Pauli limit, but it does imply that there is a significant effect from the strong spin-orbit interaction of Ir 5d electrons in the noncentrosymmetric crystal structure. Electronic structure calculations show an interesting feature of ScIrP, where both the Sc 3d and Ir 5d orbitals contribute to the electronic density of states at the Fermi level.Elemental Ca and Sc show superconductivity with a relatively high transition temperature T c of ~20 K at high pressures. Ca is not a superconductor at ambient pressure but becomes superconducting above ~50 GPa [1]. T c increases with increasing pressure and exceeds 20 K at ~100 GPa [2], which is the highest T c in all elemental metals. Sc exhibits a superconducting transition above ~60 GPa, which approaches 20 K at 107 GPa [3,4]. At higher pressures, however, Sc undergoes a structural phase transition to a nonsuperconducting phase (Sc-III). If this transition did not occur, Sc would exhibit a T c higher than 20 K. In simple-metal superconductors such as Al, Sn, and Pb, T c decreases with increasing pressure due to a decrease of the electronic density of states (DOS). The pressure effects on T c in Ca and Sc, opposite to those in simple metals, have been discussed in terms of the pressure-induced s−d electron transfer where 4s electrons are dominant for electron conduction at ambient pressure and are transferred to the narrower 3d band by applying pressure [4,5]. The electrons occupying the 3d band play an important role in relatively high T c superconductivity.

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Superconductivity under high pressure in the binary compoundCaLi2

Cited by 30 publications

References 34 publications

Magnetism of europium under extreme pressures

Magnetism of europium under extreme pressures

Competing phases, strong electron-phonon interaction, and superconductivity in elemental calcium under high pressure

Superconductivity in the Hexagonal Ternary Phosphide ScIrP

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