Untitled

Drechsler, S.‐L.; Rösner, H.; Shulga, S. V.; Fuchs, G.; Lips, H. von; Freudenberger, J.; Golden,; Knupfer, M.; Müller, K.‐H.

doi:10.1023/a:1022563716127

Cited by 10 publications

(3 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…an effective two-band model [30]. T c and γ N are reduced to a smaller extent, which has been ascribed to a slight reduction of the electron-phonon coupling constant λ at intermediate x [33,34]. For T c a dip near x = 0.7 is observed, in accordance with refs.…”

Section: Resultssupporting

confidence: 88%

Specific heat and disorder in the mixed state of non-magnetic borocarbides

et al. 2002

View full text Add to dashboard Cite

62.Dh -rare earth and transition metal substitution. PACS. 74.25.Bt -specific heat.Abstract. -The temperature and magnetic field dependence of the specific heat cp(T, H) in the superconducting mixed state as well as the upper critical field H c2 (T ) have been measured for polycrystalline YxLu 1−x Ni 2 B 2 C and Y(Ni 1−y Pty) 2 B 2 C samples. The linear-in-T electronic specific heat contribution γ(H) · T exhibits significant deviations from the usual linear-in-H law for all x and y the transition metal site (T ) resulting in a disorder dependent negative curvature of γ(H). The deviations from that linear behaviour of our unsubstituted samples are the largest reported so far for any superconductor. The H c2 (T ) data point to the quasi-clean limit for (Y,Lu)-substitutions and to a transition to the quasi-dirty limit for (Ni,Pt)-substitutions. The γ(H) dependence is discussed in the unitary d-wave as well as in the quasi-clean s-wave limits. From a consideration of γ(H) data only, d-wave pairing cannot be ruled out.

show abstract

Section: Resultssupporting

confidence: 88%

Specific heat and disorder in the mixed state of non-magnetic borocarbides

et al. 2002

View full text Add to dashboard Cite

show abstract

“…The unusual positive curvature of H c2 (T ) near T c observed here can be explained for superconductors in the clean limit by a significant dispersion of the Fermi velocities using, e.g., an effective two-band model [33]. T c and γ N are reduced to a smaller extent, which has been ascribed to a slight reduction of the electron-phonon coupling constant λ at intermediate x [34,35]. For T c a dip near x = 0.7 is observed, in accordance with refs.…”

Section: Resultsmentioning

confidence: 75%

Specific heat and disorder in the mixed state of non-magnetic borocarbides

et al. 2002

View full text Add to dashboard Cite

The temperature and magnetic-field dependence of the specific heat cp(T, H) in the superconducting (sc) mixed state as well as the upper critical field Hc2(T ) have been measured for polycrystalline YxLu1−xNi2B2C and Y(Ni1−yPty)2B2C samples. The linear-in-T electronic specific-heat contribution γ(H) • T exhibits significant deviations from the usual linear-in-H law resulting in a disorder-dependent negative curvature of γ(H). The Hc2(T ) data point to the quasi-clean limit for (Y, Lu)-substitutions and to a transition to the quasi-dirty limit for (Ni, Pt)-substitutions. The γ(H)-dependence is discussed in the unitary d-wave as well as in the quasi-clean s-wave limits. From a consideration of γ(H) data only, d-wave pairing cannot be ruled out.

show abstract

“…We start with (i) the nonmagnetic borocarbide YNi 2 B 2 C (T c = 15.6 K). According to Widder et al [96] one has Ωp = 4.25 eV for the plasma frequency already renormalized by the el-ph interaction and λ opt = 1.2 in accord with the Fermi surface averaged λ = 1.05 from specific heat data [97]. Using the penetration depth λ L (0) ≈ λ L (T = 3K) = 58 nm from the µSR data by Ohishi et al [98], one arrives at (1 + δ) = 1.56.…”

Section: Comparison With Other Exotic Superconductorsmentioning

confidence: 91%

Insight into the physics of Fe-pnictides from optical and T= 0 penetration depth data

Drechsler

Roth

Grobosch

et al. 2010

Physica C: Superconductivity and its Applications

Self Cite

View full text Add to dashboard Cite

We report theoretical values for the unscreened plasma frequencies Ω p of several Fe pnictides obtained from density functional theory (DFT) based calculations within the local density approximation (LDA) and compare them with experimental plasma frequencies obtained from reflectivity measurements on both polycrystalline samples and single crystals. The sizable renormalization observed for all considered compounds points to the presence of significant many-body effects beyond the LDA. From the large values of the empirical background dielectric constant ε ∞ ≈ 12-15 derived from reflectivity data, we estimate a large arsenic polarizabilityα As ≈ 9.5 ± 1.2Å 3 where the details depend on the polarizabilities of the remaining ions taken from the literature. This large polarizability can significantly reduce the value of the Coulomb repulsion U d ∼4 eV on iron known from iron oxides to a level of 2 eV or below. In general, independently on such details, this result points to rather strong polaronic effects as suggested by G.A. Sawatzky et al., in references arXiv:0808.1390 [11] and arXiv:0811.0214 [12]. Possible consequences for the conditions of a formation of bipolarons are discussed, too. From the extrapolated µSR (muon spin rotation) penetration depth data at very low-temperature and the experimental value of the unscreened plasma frequency we estimate the total coupling constant λ tot for the electron-boson interaction within the framework of the Eliashberg-theory adopting an effective single band approximation. For LaFeAsO 0.9 F 0.1 a weak to intermediately strong coupling regime and a quasi-clean limit behaviour are found. For a pronounced multiband case we obtain a constraint for various intraband coupling constants which in principle allows for a sizable strong coupling in bands with either slow electrons or holes.

show abstract

Untitled

Cited by 10 publications

References 8 publications

Specific heat and disorder in the mixed state of non-magnetic borocarbides

Specific heat and disorder in the mixed state of non-magnetic borocarbides

Specific heat and disorder in the mixed state of non-magnetic borocarbides

Insight into the physics of Fe-pnictides from optical and T= 0 penetration depth data

Contact Info

Product

Resources

About