Invited review: Graphite and its hidden superconductivity

Esquinazi, P.

doi:10.4279/pip.050007

Cited by 23 publications

(34 citation statements)

References 89 publications

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“…Additional evidence was then sought by plotting the difference of the two magnetization signals (mFC-mZFC) following the method reported by Scheike et al [7,8]. These analyses revealed a non-zero trend in conditions of large field values of 5000 Oe and 10000 Oe [35][36][37]. This observation seems to confirm the complex nature of the signal shown in figure 5.…”

Section: Resultsmentioning

confidence: 57%

“…Furthermore, no significant overlap between the FC and ZFC signals was observed, despite the used high fields values (i.e. significant overlap would be expected for a standard ferromagnetic component for applied fields above the H saturation [35][36][37]). Additional evidence was then sought by plotting the difference of the two magnetization signals (mFC-mZFC) following the method reported by Scheike et al [7,8].…”

Section: Resultsmentioning

confidence: 92%

“…Indeed, a previous work has shown presence of contamination on surface layers of commercially available HOPG [33]. [35][36][37] have shown that a finite positive difference between mFC -mZFC can be possibly attributed as due to pinning of magnetic entities, superconducting vortices or magnetic domains in ferromagnets in conditions of low applied magnetic field values. Such a subtraction would be however expected to sharply decrease to zero in conditions of applied magnetic field larger than saturation-fields for H>H saturation .…”

Section: Resultsmentioning

confidence: 99%

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Magnetic vortex and unsaturated magnetization components in highly oriented pyrolytic graphite

Taallah

Xia

Guo

et al. 2020

Mater. Res. Express

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Observation of ferromagnetic and granular superconductive features in highly-oriented-pyrolyticgraphite (HOPG) has recently attracted an important attention. We report a novel temperature dependent XRD and SQUID investigation of HOPG in the temperature range from 300.15 to 77.15 K. Unusual hysteresis features indicate the possible presence of vortex states in conditions of magnetic field approximately perpendicular to the HOPG layers. This interpretation is further supported by additional measurements performed on intermediate lamellae extracted by exfoliation. Evidence of a possible structural-transition in the c-axis of HOPG in the temperature range between 77 K and 100K is also provided by using the Rietveld refinement method. ZFC and FC measurements performed at high field values of 5000-10000 Oe, together with mFC-mZFC subtraction, highlight absence of a sharp depletion of the difference between magnetization signals towards zero. These observations may indicate the possible presence of additional unsaturated weak features, which are ascribed to superconductive signals as previously predicted by Scheike et al (Scheike et al 2013 Carbon; 59:140).

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Section: Resultsmentioning

confidence: 57%

Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

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Magnetic vortex and unsaturated magnetization components in highly oriented pyrolytic graphite

Taallah

Xia

Guo

et al. 2020

Mater. Res. Express

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“…The high fields increase of the TH is not compatible with any known magnetic order in carbon-based ferromagnetic Finally, magnetization measurements done on bulk highly oriented pyrolytic graphite samples of high grade with interfaces, see Section III, show similar behavior as for the water-treated graphite powder, in contrast to a bulk HOPG sample without or less density of interfaces [8]. Several others experimental studies partially reviewed in [17,18] indicate that superconductivity is embedded in certain interfaces of the graphite structure. Structural evidence for the existence of interfaces is presented in the next section.…”

Section: Magnetization Measurements On Graphite Powdersmentioning

confidence: 92%

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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“…Commentary on "Graphite and its hidden superconductivity" E. M. Forgan 1 * I write this comment on the article by Esquinazi [1] as an expert on superconductivity but not as an expert on graphite. I should also mention that in 1986, a student asked me what I thought about a paper written by Bednorz & Muller in Z. Phys.…”

Section: Issn 1852-4249mentioning

confidence: 99%