Superconductivity and Antiferromagnetism in Boron-Rich Lattices

Matthias, B. T.; Geballe, T. H.; Andres, K.; Corenzwit, E.; Hull, G. W.; Maita, J. P.

doi:10.1126/science.159.3814.530

Cited by 260 publications

(127 citation statements)

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“…Phases II and IV are associated with the two multipolar phases with AFQ and octupolar ordering. The "SC" dome at the bottom-right corner schematically indicates the dubious superconducting phase of the pure LaB 6 [31,[48][49][50]. Phases III, V and VI are three different types of AFM ordering, realized in Ce 1−x Nd x B 6 .…”

Section: Introductionmentioning

confidence: 99%

Doping-induced redistribution of magnetic spectral weight in the substituted hexaborides Ce1−xLaxB6 and
Nikitin
¹
,
Portnichenko
²
,
Dukhnenko
³

et al. 2018
Phys. Rev. B
12
3
16
0
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We investigate the doping-induced changes in the electronic structure of CeB 6 on a series of substituted Ce 1−x R x B 6 samples (R = La, Nd) using diffuse neutron scattering. We observe a redistribution of magnetic spectral weight across the Brillouin zone, which we associate with the changes in the Fermi-surface nesting properties related to the modified charge carrier concentration. In particular, a strong diffuse peak at the corner of the Brillouin zone (R point), which coincides with the propagation vector of the elusive antiferroquadrupolar (AFQ) order in CeB 6 , is rapidly suppressed by both La and Nd doping, like the AFQ order itself. The corresponding spectral weight is transferred to the X (00 1 2 ) point, ultimately stabilizing a long-range AFM order at this wave vector at the Nd-rich side of the phase diagram. At an intermediate Nd concentration, a broad diffuse peak with multiple local maxima of intensity is observed around the X point, evidencing itinerant frustration that gives rise to multiple ordered phases for which Ce 1−x Nd x B 6 is known. On the La-rich side of the phase diagram, however, dilution of the magnetic moments prevents the formation of a similar (00 1 2 )-type order despite the presence of nesting. Our results demonstrate how diffuse neutron scattering can be used to probe the nesting vectors in complex f-electron systems directly, without reference to the single-particle band structure, and emphasize the role of Fermi surface geometry in stabilizing magnetic order in rare-earth hexaborides.

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Section: Introductionmentioning

confidence: 99%

Doping-induced redistribution of magnetic spectral weight in the substituted hexaborides Ce1−xLaxB6 and
Nikitin
¹
,
Portnichenko
²
,
Dukhnenko
³

et al. 2018
Phys. Rev. B
12
3
16
0
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“…2 In the crystal, Zr atoms are surrounded by 24 boron atoms arranged on a truncated octahedron and has the smallest lattice constant (space group 3,4 Fm3m; a ¼ 7:4075Å) of all known dodecaborides. 5 Scanning tunneling spectroscopy and magnetization measurements show that ZrB 12 single crystal has excellent surface properties.…”

Section: Introductionmentioning

confidence: 99%

Surface bulk differences in a conventional superconductor, ZrB12

Thakur

Biswas

Sahadev

et al. 2013

Journal of Applied Physics

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We studied the electronic structure of a conventional superconductor, ZrB 12 , using high resolution x-ray photoemission spectroscopy and single crystalline samples. Experimental results with different bulk sensitivity reveal boron deficiency at the surface while the bulk is stoichiometric and different valence states of Zr at the surface relative to those in the bulk. Signature of satellite features is observed in the Zr core level spectra corresponding to the bulk of the material suggesting importance of electron correlation among the conduction electrons in the bulk while the surface appears to be uncorrelated. These results provide an insight on surface-bulk differences, which is important for fabrication of devices based on such superconductors. V C 2013 AIP Publishing LLC.

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“…[2] that nonadiabatic character can be further enhanced by low charge carrier density, that is the case for ZrB 12 [4,5].…”

mentioning

confidence: 99%

Anomalous electron-phonon coupling probed on the surface of superconductorZrB12

et al. 2005

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Magnetization measurements under hydrostatic pressure up to 10.5 kbar in zirconium dodecaboride ZrB12 superconductor (Tc ≃ 6.0 K at p = 0) were carried out. A negative pressure effect on Tc with dTc/dp = −0.0225(3) K/kbar was observed. The electron-phonon coupling constant λ el−ph decreases with increasing pressure with d ln λ el−ph /dp ≃ −0.20%/kbar. The magnetic field penetration depth λ was studied in the Meissner state and, therefore, probes only the surface of the sample. The absolute values of λ and the superconducting energy gap at ambient pressure and zero temperature were found to be λ(0) =140(30) nm and ∆0 =1.251(9) meV, respectively. ∆0 scales linearly with Tc as 2∆0/kBTc = 4.79(1). The studies of the pressure effect on λ reveal that λ −2 increases with pressure with d ln λ −2 (0)/dp = 0.60(23) %/kbar. This effect can not be explained within the framework of conventional adiabatic electron-phonon pairing, suggesting that close to the surface, an unconventional non-adiabatic character of the electron-phonon coupling takes place.PACS numbers: 74.70. Ad, 74.62.Fj, 74.25.Ha, 83.80.Fg The traditional concept of superconductivity is strictly associated with the electron-phonon interaction. The conventional theory is based on the Migdal-Eliashberg adiabatic approximation [1] that, in fact, leads to the prediction of many peculiar features which are a direct evidence of a phonon mediated superconductivity. The adiabatic approximation is valid if the parameter ω 0 /E f is small (ω 0 is the relevant phonon frequency and E f is the Fermi energy). Usually this parameter is regarded as a measure of nonadibaticity. However, crossover from a conventional adiabatic to an unconventional nonadiabatic regime does not depend only on the value of the ω 0 /E f ratio. Paci et al. [8] show that even in a case of small "adiabatic" ratio one would expect the nonadiabatic coupling in superconductors having high value of the electron-phonon coupling constant λ el−ph . Among BCS superconductors the zirconium dodecaboride (ZrB 12 ) is probably a candidate for the observation of such type of anomalous coupling. It stems from the rather small value of the Fermi energy ∼1 eV [3] that, together with the Debye temperature ∼20 meV [4], leads to a ratio ω 0 /E f ∼0.02. A strong coupling ratio 2∆/k B T c ≃ 4.8 was observed by surface sensitive techniques [3,6]. This suggests that the electron-phonon coupling constant, which has a bulk value λ el−ph ≃ 0.67 [3], increases at the surface. From the comparison with strong coupled metallic superconductors [7] one would expect λ surf.el−ph ≃ 1.7 − 1.9. Moreover, it was pointed out by Cappelluti et al.[2] that nonadiabatic character can be further enhanced by low charge carrier density, that is the case for ZrB 12 [4,5].One of the key feature of nonadiabatic superconductivity is the observation of unconventional isotope and pressure effects on the magnetic field penetration depth λ. Note, that in adiabatic superconductors (or in the superconductors where the nonadiabatic effects are small) the...

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Superconductivity and Antiferromagnetism in Boron-Rich Lattices

Abstract: Ferromagnetism, antiferromagnetism, or superconductivity has been discovered in most hexa- and dodecaborides.

Cited by 260 publications

References 5 publications

Doping-induced redistribution of magnetic spectral weight in the substituted hexaborides Ce1−xLaxB6 and
Nikitin
¹
,
Portnichenko
²
,
Dukhnenko
³

et al. 2018
Phys. Rev. B
12
3
16
0
View full text Add to dashboard Cite

Doping-induced redistribution of magnetic spectral weight in the substituted hexaborides Ce1−xLaxB6 and
Nikitin
¹
,
Portnichenko
²
,
Dukhnenko
³

et al. 2018
Phys. Rev. B
12
3
16
0
View full text Add to dashboard Cite

Surface bulk differences in a conventional superconductor, ZrB12

Anomalous electron-phonon coupling probed on the surface of superconductorZrB12

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Superconductivity and Antiferromagnetism in Boron-Rich Lattices

Abstract: Ferromagnetism, antiferromagnetism, or superconductivity has been discovered in most hexa- and dodecaborides.

Cited by 260 publications

References 5 publications

Doping-induced redistribution of magnetic spectral weight in the substituted hexaborides Ce1−xLaxB6 and Nikitin1, Portnichenko2, Dukhnenko3 et al. 2018Phys. Rev. B123160View full textAdd to dashboardCite

Doping-induced redistribution of magnetic spectral weight in the substituted hexaborides Ce1−xLaxB6 and Nikitin1, Portnichenko2, Dukhnenko3 et al. 2018Phys. Rev. B123160View full textAdd to dashboardCite

Surface bulk differences in a conventional superconductor, ZrB12

Anomalous electron-phonon coupling probed on the surface of superconductorZrB12

Contact Info

Product

Resources

About

Doping-induced redistribution of magnetic spectral weight in the substituted hexaborides Ce1−xLaxB6 and
Nikitin
¹
,
Portnichenko
²
,
Dukhnenko
³

et al. 2018
Phys. Rev. B
12
3
16
0
View full text Add to dashboard Cite

Doping-induced redistribution of magnetic spectral weight in the substituted hexaborides Ce1−xLaxB6 and
Nikitin
¹
,
Portnichenko
²
,
Dukhnenko
³

et al. 2018
Phys. Rev. B
12
3
16
0
View full text Add to dashboard Cite