Advanced Quantum Technologies is a peer reviewed journal that has published a paper – Global Room-Temperature Superconductivity in Graphite. The researchers are from Brazil, Italy and Switzerland.
They use the scotch-taped cleaved pyrolytic graphite carrying the wrinkles that resulted from this cleaving to which they also refer as to line defects. They detected experimental evidence for the global zero-resistance state. The experimental data clearly demonstrated that the array of nearly parallel linear defects that form due to the cleaving of the highly oriented pyrolytic graphite hosts one-dimensional superconductivity.
One-Dimensional room temperture and room pressure superconductivity is what part of the theory and claims proposed for LK99 and sulfurized LK99 and PCPOSOS.
Room temperature superconductivity under normal conditions has been a major challenge of physics and material science since its discovery. Here the global room-temperature superconductivity observed in cleaved highly oriented pyrolytic graphite carrying dense arrays of nearly parallel surface line defects is reported. The multiterminal measurements performed at the ambient pressure in the temperature interval 4.5 K ≤ T ≤ 300 K and at magnetic fields 0 ≤ B ≤ 9 T applied perpendicular to the basal graphitic planes reveal that the superconducting critical current Ic(T, B) is governed by the normal state resistance RN(T, B) so that Ic(T, B) is proportional to 1/RN(T, B). Magnetization M(T, B) measurements of superconducting screening and hysteresis loops together with the critical current oscillations with temperature that are characteristic for superconductor-ferromagnet-superconductor Josephson chains, provide strong support for the occurrence of superconductivity at T over 300 K. A theory of global superconductivity emerging in the array of linear structural defects is developed which well describes the experimental findings and demonstrate that global superconductivity arises as a global phase coherence of superconducting granules in linear defects promoted by the stabilizing effect of underlying Bernal graphite via tunneling coupling to the three dimensional (3D) material.
The mercury-based cuprate HgBa2Ca2Cu3O9 shows the highest Tc = 135 K under the ambient pressure for the accepted uncontroversial best.
Graphite is yet another promising material taking part in a race for the RTSC (room temperature superconductor). Decades ago, Antonowicz measured the Josephson-type oscillations and Shapiro-like steps in current-voltage, I–V, characteristics at T=300 K in Al-AC-Al sandwiches, where the AC stands for the amorphous carbon. Various experimental groups have also reported localized superconductivity in graphite at temperatures as high as 300 K. Because the AC consists of curved graphene and/or fullerene-like fragments, one can justly assume that similar structural defects in graphite may be responsible for the occurrence of high-temperature localized superconducting regions. However, so far, all the efforts to achieve a global superconductivity at elevated temperatures in graphite failed.
In the present work, researchers report the first unambiguous experimental evidence for the global zero-resistance state, RTSC, in the scotch-tape cleaved highly oriented pyrolytic graphite (HOPG) that possesses dense arrays of nearly parallel line defects (LD), the wrinkles.
They measured the I–V characteristics at T = 300 K (aka room temperature and room pressure). The data demonstrate the zero-resistance state below the magnetic-field-dependent critical current Ic(B), which is decreasing with the field. The obtained I–V curves demonstrate the characteristic features of low-dimensional superconductors. First, the excess voltage peaks seen just above the Ic(B) and before the Ohmic regime sets in at I> IN, see Figure 1c, are similar to those measured in 1D or 2D superconducting constrictions, and are attributed to the charge imbalance and/or presence of phase slip (PS) centers at superconductor (S) –normal metal (N) interfaces. The onset of the Ohmic behavior in I–V characteristics corresponds to the suppression of the non-equilibrium superconducting regime or the transition to the normal state.
Conclusion
They have reported the first-ever observation of the global room-temperature superconductivity at ambient pressure. Notably, while a single graphite layer, graphene, is hailed as a miracle material of the new century, the bulk pyrolytic graphite opens the way to even more spectacular advances in technology. The experimental data clearly demonstrated that the array of nearly parallel linear defects that form due to the cleaving of the highly oriented pyrolytic graphite hosts one-dimensional superconductivity. The measurements at the ambient pressure at temperatures up to 300 K and applied magnetic field perpendicular to the basal graphitic planes up to 9 T, reveal that the superconducting critical current Ic(T, B) is proportional to 1/RN(T, B), indicating the Josephson-junction like nature of the emerging superconductivity. This latter conclusion is supported by the oscillations of the critical current with temperature that are characteristic of superconductor-ferromagnet-superconductor Josephson junctions. Global superconductivity arises due to global phase coherence in the superconducting granules array promoted by the stabilizing effect of underlying Bernal graphite having the resistance RN. The theory of global superconductivity emerging on the array of linear structural defects well describes the experimental findings.
The ideas and concepts explored in our work are not confined to graphite. The theoretical model is quite general and guides where to look for more room-temperature superconducting materials. The basic principle they have uncovered is that linear defects in stacked materials host strong strain gradient fluctuations, which induce the local pairing of electrons into condensate droplets that form JJA-like structures in the planes. The global superconductivity is then established by the effect of the tunneling links connecting the superconducting droplets. If the droplets are sufficiently small, one foresees a fairly high critical superconducting temperature.
Impact Factory of 4.4 is in the top 10% of journals.
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