Superconductivity of hexagonal beryllium

Falge, R. L.

doi:10.1016/0375-9601(67)90624-x

Cited by 35 publications

(20 citation statements)

References 8 publications

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“…Although it cannot be classified as an unconventional superconductor, ReBe 22 is far away also from the region of conventional superconductors and shows practically the same ratio as the multiband superconductor LaNiC 2 (both lying in the same dashed-dotted line). Compared to pure Be ( =´=´-T T 0.026 1.64 10 1.58 10 c F 5 7 ) [1,30], the T c /T F value of ReBe 22 is enhanced due to the presence of diluted Re, the latter being characterized by a lower Fermi temperature and, hence, by a larger T T c F ratio (see Re in figure 13). Such conclusion is further supported by our electronic band-structure calculations, which show that, although Re contributes only 4% to the atomic ratio, with its 12% weight, it is over-represented in the DOS at the Fermi level.…”

Section: Discussionmentioning

confidence: 99%

“…As one of the lightest elements, beryllium exhibits high-frequency lattice vibrations, a condition for achieving superconductivity (SC) with a sizeable critical temperature. Yet, paradoxically, its T c =0.026 K is so low [1], that its SC is often overlooked. Clearly, T c is affected also by the electron-phonon coupling strength (typically large in elements with covalent-bonding tendencies) and the density of states (DOS) at the Fermi level N(ò F ) (rather low in pure Be).…”

Section: Introductionmentioning

confidence: 99%

“…Temperature dependence of the electrical resistivity of ReBe22 . The solid line through the data is a fit to equation(1). The inset shows the data in the low-temperature region, highlighting the superconducting transition.…”

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confidence: 99%

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Enhanced T_c and multiband superconductivity in the fully-gapped ReBe₂₂ superconductor

et al. 2019

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In search of the origin of superconductivity (SC) in diluted rhenium superconductors and their significantly enhanced T c compared to pure Be (0.026 K), we investigated the intermetallic ReBe 22 compound, mostly by means of muon-spin rotation/relaxation (μSR). At a macroscopic level, its bulk SC (with T c =9.4 K) was studied via electrical resistivity, magnetization, and heat-capacity measurements. The superfluid density, as determined from transverse-field μSR and electronic specific-heat measurements, suggest that ReBe 22 is a fully-gapped superconductor with some multigap features. The larger gap value, D = 1.78 l 0 T k B c , with a weight of almost 90%, is slightly higher than that expected from the BCS theory in the weak-coupling case. The multigap feature, rather unusual for an almost elemental superconductor, is further supported by the field-dependent specific-heat coefficient, the temperature dependence of the upper critical field, as well as by electronic bandstructure calculations. The absence of spontaneous magnetic fields below T c , as determined from zero-field μSR measurements, indicates a preserved time-reversal symmetry in the superconducting state of ReBe 22 . In general, we find that a dramatic increase in the density of states at the Fermi level and an increase in the electron-phonon coupling strength, both contribute to the highly enhanced T c value of ReBe 22 .

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enhanced T_c and multiband superconductivity in the fully-gapped ReBe₂₂ superconductor

et al. 2019

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“…As a matter of fact, most of the elements having T c higher than 4 K at ambient pressure are heavy elements (see Table 1 ). On the other hand, light elements usually have very low T c at ambient pressure; T c 's of lithium (Li) and beryllium (Be) are just 0.4 mK and 0.026 K, respectively. This fact seems to suggest that light‐element materials have little chance to be a high‐ T c superconductor.…”

Section: Introductionmentioning

confidence: 99%

Nonempirical Calculation of Superconducting Transition Temperatures in Light‐Element Superconductors

et al. 2017

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Recent progress in the fully nonempirical calculation of the superconducting transition temperature (T ) is reviewed. Especially, this study focuses on three representative light-element high-T superconductors, i.e., elemental Li, sulfur hydrides, and alkali-doped fullerides. Here, it is discussed how crucial it is to develop the beyond Migdal-Eliashberg (ME) methods. For Li, a scheme of superconducting density functional theory for the plasmon mechanism is formulated and it is found that T is dramatically enhanced by considering the frequency dependence of the screened Coulomb interaction. For sulfur hydrides, it is essential to go beyond not only the static approximation for the screened Coulomb interaction, but also the constant density-of-states approximation for electrons, the harmonic approximation for phonons, and the Migdal approximation for the electron-phonon vertex, all of which have been employed in the standard ME calculation. It is also shown that the feedback effect in the self-consistent calculation of the self-energy and the zero point motion considerably affect the calculation of T . For alkali-doped fullerides, the interplay between electron-phonon coupling and electron correlations becomes more nontrivial. It has been demonstrated that the combination of density functional theory and dynamical mean field theory with the ab initio downfolding scheme for electron-phonon coupled systems works successfully. This study not only reproduces the experimental phase diagram but also obtains a unified view of the high-T superconductivity and the Mott-Hubbard transition in the fullerides. The results for these high-T superconductors will provide a firm ground for future materials design of new superconductors.

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“…Be is a superconductor, albeit with a surprisingly low transition temperature T c (considering that its Debye temperature is exceedingly high). [12] Boron is a semiconductor but becomes a metal and also a superconductor at very high pressures. [13] Both elements have their applications: beryllium as window material in Xray equipment, as a wall liner in plasma fusion reactors, [14] or as a stiff lightweight material in aerospace applications; boron as a neutron moderator in nuclear reactors, or as a superhard material by itself or as a key ingredient in alloys.…”

Section: Introductionmentioning

confidence: 99%

Binary Compounds of Boron and Beryllium: A Rich Structural Arena with Space for Predictions

Hermann

Ashcroft

Hoffmann

2013

Chemistry A European J

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We explore ground-state structures and stoichiometries of the Be-B system in the static limit, with Be atom concentrations of 20 % or greater, and from P = 1 atm up to 320 GPa. At P = 1 atm, predictions are offered for several known compounds, the structures of which have not yet been determined experimentally. Specifically, at 1 atm, we predict a structure of R3m symmetry for the compound Be2B3, seen experimentally at high temperatures, which contains interesting BeBBBBe rods; and for the compound BeB4 we calculate metastability with respect to the elements with a structure similar to MgB4, which is quickly replaced as the pressure is elevated by a Cmcm structure that features 6- and 4-membered rings in B cages, with Be interstitials. For another high-temperature compound, Be2B, we confirm the CaF2 structure, but find a competitive and actually slightly more stable ground-state structure of C2/m symmetry that features B2 pairs. In the case of BeB2, a material for which the stoichiometry has been the subject of debate, we have a clear prediction of a stable F43m structure at P=1 atm. It has a diamondoid structure that is based on cubic (lower P) or hexagonal (higher P) diamond networks of B, but with Be in the interstices. This Zintl structure is a semiconductor at low and intermediate pressures. At higher pressures, BeB2 dominates the phase diagram. In general, the Zintl-Klemm concept of effective electron transfer from the more electropositive ion and bond formation among the resulting anions has proven useful in analyzing the structural preferences of many compositions in the Be-B system at P=1 atm and at elevated pressures. An unusual feature of this binary system is that the 1:1 BeB stoichiometry never appears to reach stability in the static limit, although it comes close, as does Be17B12. Also stable at high pressures are stoichiometries BeB3, BeB4, and Be5B2.

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Superconductivity of hexagonal beryllium

Cited by 35 publications

References 8 publications

Enhanced T_c and multiband superconductivity in the fully-gapped ReBe₂₂ superconductor

Enhanced T_c and multiband superconductivity in the fully-gapped ReBe₂₂ superconductor

Nonempirical Calculation of Superconducting Transition Temperatures in Light‐Element Superconductors

Binary Compounds of Boron and Beryllium: A Rich Structural Arena with Space for Predictions

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Superconductivity of hexagonal beryllium

Cited by 35 publications

References 8 publications

Enhanced Tc and multiband superconductivity in the fully-gapped ReBe22 superconductor

Enhanced Tc and multiband superconductivity in the fully-gapped ReBe22 superconductor

Nonempirical Calculation of Superconducting Transition Temperatures in Light‐Element Superconductors

Binary Compounds of Boron and Beryllium: A Rich Structural Arena with Space for Predictions

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Enhanced T_c and multiband superconductivity in the fully-gapped ReBe₂₂ superconductor

Enhanced T_c and multiband superconductivity in the fully-gapped ReBe₂₂ superconductor