Indications for intrinsic superconductivity in highly oriented pyrolytic graphite

Esquinazi, P.; Garcı́a, N.; Barzola‐Quiquia, J.; Rödiger, P.; Schindler, Kathrin; Yao, Jane; Ziese, M.

doi:10.1103/physrevb.78.134516

Cited by 48 publications

(64 citation statements)

References 34 publications

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“…Recently done study of the behavior of the MR of multigraphene samples suggests the existence of granular superconductivity [6]. The main experimental evidence comes from the anomalous irreversible behavior of the MR, which appears compatible with Josephson-coupled superconducting grains [6]. We note that Bi, as graphite, has a low density, low effective mass of carriers and huge values of the electron mean free path [24,25].…”

Section: Figurementioning

confidence: 99%

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Sample size effects on the transport characteristics of mesoscopic graphite samples

Barzola‐Quiquia

Yao

Rödiger

et al. 2008

Physica Status Solidi (a)

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145

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In this work we investigated correlations between the internal microstructure and sample size (lateral as well as thickness) of mesoscopic, tens of nanometer thick graphite (multigraphene) samples and the temperature (T ) and field (B) dependence of their electrical resistivity ρ(T, B). Low energy transmission electron microscopy reveals that the original highly oriented pyrolytic graphite material -from which the multigraphene samples were obtained by exfoliation -is composed of a stack of ∼ 50 nm thick and micrometer long crystalline regions separated by interfaces running parallel to the graphene planes. We found a qualitative and quantitative change in the behavior of ρ(T, B) upon thickness of the multigraphene samples, indicating that their internal microstructure is important.The overall results indicate that the metallic-like behavior of ρ(T ) at zero field measured for bulk graphite samples is not intrinsic of ideal graphite. The results suggest that the interfaces between crystalline regions may be responsible for the superconducting-like properties observed in graphite. Our transport measurements also show that reducing the sample lateral size as well as the length between voltage electrodes decreases the magnetoresistance, in agreement with recently published results. The magnetoresistance of the multigraphene samples shows a scaling of the form ((R(B) − R(0))/R(0))/T α = f (B/T ) with a sample dependent exponent α ∼ 1, which applies in the whole temperature 2 K ≤ T ≤ 270 K and magnetic field range B ≤ 8 T.

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Section: Figurementioning

confidence: 99%

“…The possibility of superconductivity in graphite has been discussed in recent years, see Refs. [7,6] for further reading.…”

Section: Figurementioning

confidence: 99%

Sample size effects on the transport characteristics of mesoscopic graphite samples

Barzola‐Quiquia

Yao

Rödiger

et al. 2008

Physica Status Solidi (a)

Self Cite

145

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“…To date, a significant number of indirect experiments indicating the existence of a superconducting state up to room temperature in graphite-based compounds have been reported [8][9][10][11][12]. The main problem of these indirect observations lies in the fact that the superconducting regions occupy only a small areas of carbon materials, and for this reason, the observable effects of superconductivity are negligible in bulk samples [9]. Evidence for superconductivity in graphite lamellae at temperatures above 150 K has been demonstrated in [13].…”

Section: Introductionmentioning

confidence: 99%

Correlation between structure and resistance of composites based on polystyrene and multilayered graphene oxide

Nikolaeva¹,

Ананьева²,

Bugrov³

et al. 2017

Nanosystems: Phys. Chem. Math.

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“…Although signs of granular superconductivity in the electrical resistance of graphite samples with electrodes on the main surface (usually on the top graphene layer) have been recognized in earlier studies [39,40], if we could contact directly the edges of the interfaces found in graphite samples we expect to observe more clear signs of Josephson or granular superconducting behavior in the transport measurements. As it became evident from the results shown in Fig.…”

Section: Contacting the Interface Edges In Tem Lamellaementioning

confidence: 94%

Evidence for room temperature superconductivity at graphite interfaces

Esquinazi

Precker

Stiller

et al. 2017

Quantum Stud.: Math. Found.

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In the last 43 years several hints were reported suggesting the existence of granular superconductivity above room temperature in different graphite-based systems. In this paper some of the results are reviewed, giving special attention to those obtained in water and n-heptane treated graphite powders, commercial and natural bulk graphite samples with different characteristics as well as transmission electron microscope (TEM) lamellae. The overall results indicate that superconducting regions exist and are localized at certain internal interfaces of the graphite structure. The existence of the rhombohedral graphite phase in all samples with superconducting-like properties suggests its interfaces with the Bernal phase as a possible origin for the high-temperature superconductivity, as theoretical calculations predict. High precision electrical resistance and magnetization measurements were used to identify a transition at Tc > ∼ 350 K. To check for the existence of true zero resistance paths in the samples we used local magnetic measurements, which results support the existence of superconducting regions at such high temperatures.

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Indications for intrinsic superconductivity in highly oriented pyrolytic graphite

Cited by 48 publications

References 34 publications

Sample size effects on the transport characteristics of mesoscopic graphite samples

Sample size effects on the transport characteristics of mesoscopic graphite samples

Correlation between structure and resistance of composites based on polystyrene and multilayered graphene oxide

Evidence for room temperature superconductivity at graphite interfaces

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