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Woodfield, Brian F.; Wright, D. A.; Fisher, Robert A.; Phillips, N. E.; Tang, Hung-Jie

doi:10.1103/physrevlett.83.4622

Cited by 22 publications

(16 citation statements)

References 7 publications

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“…This ratio is ϳ2 and 5 times larger than that of Refs. [8] and [9], respectively, which are the only prior reports of a specific heat anomaly at T c in this system. This allowed us to study the magnetic field dependence of the specific heat anomaly in much greater detail.…”

Section: -1mentioning

confidence: 85%

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Anomalous Magnetic Field Dependence of the Thermodynamic Transition Line in the Isotropic Superconductor(K,Ba)BiO3

et al. 2002

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Thermodynamic (specific heat, reversible magnetization, tunneling spectroscopy) and transport measurements have been performed on high quality (K,Ba)BiO3 single crystals. The temperature dependence of the magnetic field HCp corresponding to the onset of the specific heat anomaly presents a clear positive curvature. HCp is significantly smaller than the field H∆ for which the superconducting gap vanishes but is closely related to the irreversibility line deduced from transport data. Moreover, the temperature dependence of the reversible magnetization present a strong deviation from the Ginzburg-Landau theory emphasazing the peculiar nature of the superconducting transition in this material.

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Section: -1mentioning

confidence: 85%

“…These measurements are only relative and were renormalized using the data from Ref. [8]. Figure 1 displays the temperature dependence of the specific heat at various magnetic fields up to 5 T. The 7 T curve is equal to the normal state specific heat above T T c ͑H 7 T͒ϳ20 K and has been used as a base line in Fig.…”

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confidence: 99%

Anomalous Magnetic Field Dependence of the Thermodynamic Transition Line in the Isotropic Superconductor(K,Ba)BiO3

et al. 2002

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“…The dissimilar example has been observed in Ba 1-x K x BiO 3 (Ref. 21) due to defects and the inhomogeneity of the sample. Figure 5 demonstrates the magnetic field dependence of very low temperature (≤ 5 K) specific heat as C/T vs. T 2 .…”

Section: Fig 5 C/t Vs Tmentioning

confidence: 96%

Magnetic field dependence of low-temperature specific heat of the spinel oxide superconductorLiTi2O4

et al. 2004

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Magnetic field dependence of low temperature specific heat of spinel oxide superconductor LiTi 2 O 4 has been elaborately investigated. In the normal state, the obtained electronic coefficient of specific heat ã n = 19.15 mJ/mol K 2 , the Debye temperature È D = 657 K and some other parameters are compared with those reported earlier. The superconducting transition at T c~1 1.4 K is very sharp (∆T c ~ 0.3 K) and the estimated äC/ã n T c is ~1.78. In the superconducting state, the best fit of data leads to the electronic specific heat C es /ã n T c = 9.87 exp (-1.58 T c /T) without field and ã(H) ∝ H 0.95 with fields. In addition, H c2 (0) ~ 11.7 T, H c (0)~0.32 T, ξ GL (0) ~ 55 Å , λ GL (0) ~ 1600 Å , and H c1 (0) ~ 26 mT are estimated from Werthamer-Helfand-Hohenberg (WHH) theory or other relevant relations. All results from the present study indicate that LiTi 2 O 4 can be well described by a typical type-II, BCS-like, moderate coupling, and fully gapped superconductor in the dirty limit. It is further suggested that LiTi 2 O 4 is a moderately electron-electron correlated system. 74.25.Bt, 74.25.Ha PACS number(s):

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“…Tunnelling data have shown very good agreement with BCS (isotropic gap) modelling (Sato et al 1990, Huang et al 1990, Sharifi et al 1991, Zasadzinski et al 1991, Kussmaul et al 1993, Kosugi et al 1994). The T << T c data for penetration depth (Pambianchi et al 1994) and specific heat (Woodfield et al 1999) show isotropic-gap behavior, and the optical conductivity of BKBO also looks quite conventional (Puchkov et al 1994, Timusk 1999. BKBO thus appears "anomalously conventional" in this respect.…”

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confidence: 92%

Strongly anisotropic s-wave gaps in exotic superconductors

Brandow

2003

Philosophical Magazine

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The exotic superconductors, defined as those which follow the phenomenological trend of Uemura (T c approximately µ l L -2 ), presently constitute the most broad and general class of superconductors which can reasonably be considered "similar to the high-T c cuprates". It is therefore of much interest to determine the forms of their pairing gap functions. We examine evidence for the gap forms in non-cuprate exotics, and demonstrate some general features. The cubic materials often have highly anisotropic gaps. The planar materials tend to have even stronger gap anisotropy, to the extent that they often have gap nodes, but nevertheless they usually have an s-wave-like gap symmetry. There is good evidence for the latter even in the controversial cases of planar organics and nickel borocarbides. Exceptions to these generalizations are also pointed out and discussed. §1. INTRODUCTIONThere are now many unusual superconductors which are recognized to share some of the novel features of the high-T c cuprate superconductors. The possibility of further similarity to the cuprates, in particular the possibility of pairing by exchange of a virtual spin fluctuation or paramagnon, has motivated suggestions of d-wave gap forms in some of these other superconductors, in cases where there is evidence for gap nodes. This argument has been applied especially to the planar organics and sometimes also to the 2 nickel borocarbides, in addition to the well known cases of heavy-fermion materials. This line of reasoning calls for a careful examination of the evidence for the gap forms in these and other unusual superconductors.In this paper we focus on the exotic superconductors of Uemura and co-workers. 1 These exotics include a number of the unusual superconductors of earlier (pre-cuprate) interest, as well as the cuprates themselves and others discovered after the cuprates, and they include most of the materials previously suggested as being similar to the cuprates. 2 As discussed below, they now constitute the most broad and general class of superconductors that can reasonably be considered similar to the cuprates. (The variety of crystal structures and material chemistries in this class of materials is remarkably extensive.2 ) It is therefore very reasonable to focus on these materials. We now examine many of the non-cuprate exotic materials and material families, those for which there is reasonable gap-form evidence, in order to establish two general conclusions about their superconducting phenomenology: (1) In the cubic and nearly-cubic materials, which are conventionally expected to have nearly isotropic gaps, there is often evidence of very strong gap anisotropy. Sometimes there even appear to be gap nodes, although the gap symmetry remains s-wave-like. (2) In the planar (quasi-two-dimensional) materials there are often gap nodes, but nevertheless they typically still have an s-wave-like gap symmetry.[Here s-wave-like means having the full point-group symmetry of the crystal structure, a condition which does allow the p...

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Superconducting-Normal Phase Transition in(Ba1−xKx)

Cited by 22 publications

References 7 publications

Anomalous Magnetic Field Dependence of the Thermodynamic Transition Line in the Isotropic Superconductor(K,Ba)BiO3

Anomalous Magnetic Field Dependence of the Thermodynamic Transition Line in the Isotropic Superconductor(K,Ba)BiO3

Magnetic field dependence of low-temperature specific heat of the spinel oxide superconductorLiTi2O4

Strongly anisotropic s-wave gaps in exotic superconductors

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