Determination of superconducting and normal state parameters of single crystal K3C60

Hou, J. G.; Crespi, Vincent H.; Xiang, X.‐D.; Vareka, W. A.; Briceno, G.; Zettl, A.; Cohen, Marvin L.

doi:10.1016/0038-1098(93)90831-7

Cited by 48 publications

(28 citation statements)

References 16 publications

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“…On the other hand, Palstra et al 33 estimated the coherence length to be 0 Ӎ140 Å and made the conclusion that Rb 3 C 60 is in the dirty limit. The estimate of lӍ12 Å at Tϭ0 from the upper critical field data 34,35 is also consistent with the dirty limit. Figure 7 shows the comparison of the measured L Ϫ2 (T/T c ) with the BCS dependences ͓calculated using Eq.…”

Section: ͑23͒supporting

confidence: 74%

ac susceptibility ofRb3C60fine powder

1996

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The temperature dependence of ac susceptibility (T) has been measured at different values of dc magnetic field for Rb 3 C 60 fine powder. The diamagnetic moment of the superconducting powder arises due to both screening currents in separate grains ͑intragrain contribution͒ and screening currents in clusters formed by several grains with Josephson junctions between them ͑intergrain contribution͒. The intergrain contribution of clusters is proportional to the critical current of the Josephson junctions, j c , and decreases rapidly in a dc magnetic field H, while the intragrain contribution remains unchanged up to much higher values of H. The (T) measurements at different dc magnetic fields allow us to distinguish between these two contributions and to obtain precisely the temperature dependence of the London penetration depth (T). We have found that the experimentally obtained (T) is perfectly described by the weak coupling BCS dependence in the dirty limit.

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Section: ͑23͒supporting

confidence: 74%

ac susceptibility ofRb3C60fine powder

1996

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“…The temperature coefficient of the resistivity is positive, i.e., metalliclike, and the film is a superconductor below 19 K. The resistivity just above T c is Ϸ0.5 m⍀ cm, comparable to the lowest values found in K 3 C 60 samples made from C 60 single crystals. 31 This, and the fact that the superconducting transition is not more than about 1 K wide, can be taken as an indication for the good quality of the sample.…”

Section: Resultsmentioning

confidence: 98%

Photoemission evidence of electronic stabilization of polar surfaces inK3C60

et al. 2000

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We present a detailed investigation of the surface electronic structure of solid K 3 C 60 in connection with its electronic transport properties. We find that the conductivity is extremely sensitive to the K concentration of the surface layer, and that the best-conducting samples with the highest superconducting transition temperatures have surfaces with the highest density of states at the Fermi level as measured by photoemission. The C 60 ions at the surface have, however, a valence that deviates appreciably from the 3Ϫ bulk value, namely 2.5Ϫ or even 1.5Ϫ, depending on the preparation procedure. We attribute this as being the result of an electronic rather than an atomic surface reconstruction to avoid the divergence of the electrostatic potential associated with the polar ͑111͒ surface termination of K 3 C 60 . We argue that such a mixed-valence surface should always be a metal, irrespective of whether the bulk is a metal or a Mott-Hubbard insulator.

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“…Below 100 K there is a remarkably low rise ͑4 -9 %͒ in resistivity which can be attributed to weak localization in these thin films. The weak temperature dependence of our films in comparison to K 3 C 60 single crystals, 9 which is most prominent above 300 K, is due to our limited temperature range (TϽ250 K) dictated by the parallel conduction through the substrate. The film measured with submicron contacts shows the remarkable low resistivity of 0.35ϩ0.14 m⍀ cm at 100 K, which is at least comparable to the bulk single crystal value of 0.5 m⍀ cm.…”

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confidence: 78%

“…The film measured with submicron contacts shows the remarkable low resistivity of 0.35ϩ0.14 m⍀ cm at 100 K, which is at least comparable to the bulk single crystal value of 0.5 m⍀ cm. 9 Table I lists the detailed parameters of the measurement. The films with the lower resistivity were measured with the submicron contact pattern with a probe separation of 250 nm.…”

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confidence: 99%

Single domain transport measurements ofC60films

Rogge

Durkut²,

Klapwijk³

2003

Phys. Rev. B

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Thin films of potassium doped C 60 , an organic semiconductor, have been grown on silicon. The films were grown in ultrahigh vacuum by thermal evaporation of C 60 onto oxide-terminated silicon as well as reconstructed Si͑111͒. The substrate termination had a drastic influence on the C 60 growth mode which is directly reflected in the electrical properties of the films. Measured on the single domain length scale, these films revealed resistivities comparable to bulk single crystals. In situ electrical transport properties were correlated to the morphology of the film determined by scanning tunneling microscopy. The observed excess conductivity above the superconducting transition can be attributed to two-dimensional fluctuations.

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Determination of superconducting and normal state parameters of single crystal K3C60

Cited by 48 publications

References 16 publications

ac susceptibility ofRb3C60fine powder

ac susceptibility ofRb3C60fine powder

Photoemission evidence of electronic stabilization of polar surfaces inK3C60

Single domain transport measurements ofC60films

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