[Paper Review] Superconductivity above 500 K in conductors made by bringing n-alkane into contact with graphite

Yasushi Kawashima|arXiv (Cornell University)|Dec 15, 2016

Fiber-reinforced polymer composites4 citations

TL;DR

This study reports superconductivity above 500 K in composite materials formed by contacting n-alkanes (C7–C16) with pitch-based graphite fibers, as evidenced by a sharp resistance drop during heating. Critical temperatures range from 363.08 K to 504.24 K, with transition widths as narrow as 0.15 K, suggesting high-quality superconducting behavior in these organic-inorganic heterostructures.

ABSTRACT

In 1986, a cuprate superconductor (Ba-La-Cu-O system) having a critical temperature which goes over the BCS limit (~30 K) was discovered and then a cuprate superconductor (Y-Ba-Cu-O system) with a critical temperature higher than 77 K was discovered. Furthermore, a Hg-based cuprate with a critical temperature of 133 K was found. The 133 K is still the highest critical temperature of conventional superconductors under atmospheric pressure. We have shown that materials obtained by bringing n-alkanes into contact with graphite are capable of conducting electricity with almost no energy loss at room temperature. We here report that the sudden jump in resistance showing a phase transition is observed in the materials during heating by two-probe resistance measurement. The measured critical temperatures of the materials consisting of pitch-based graphite fibers and n-alkanes having 7-16 carbon atoms range from 363.08 to 504.24 K and the transition widths range between 0.15 and 3.01 K. We also demonstrate that superconductors with critical temperatures beyond 504 K are obtained by alkanes with 16 or more carbon atoms.

Motivation & Objective

• To investigate the electrical transport properties of n-alkane/graphite composites at elevated temperatures.
• To determine whether superconducting transitions occur in these hybrid materials under ambient pressure.
• To explore the relationship between alkane chain length and critical temperature (Tc) in the composite system.
• To identify conditions under which high-Tc superconductivity can emerge in carbon-based organic-inorganic heterostructures.

Proposed method

• Preparation of pitch-based graphite fibers and their contact with n-alkanes (C7–C16) to form composite conductors.
• Two-probe resistance measurements during controlled heating cycles to detect phase transitions.
• Systematic variation of alkane chain length (C7 to C16 and beyond) to assess Tc dependence.
• Analysis of resistance vs. temperature curves to identify sharp drops indicative of superconducting transitions.
• Use of temperature-dependent resistivity data to extract critical temperature (Tc) and transition width.
• Evaluation of materials with alkanes of 16 or more carbon atoms to probe the upper limit of Tc.

Experimental results

Research questions

• RQ1 Can n-alkane/graphite composites exhibit superconductivity at temperatures exceeding 500 K?
• RQ2 How does the critical temperature (Tc) of these composites vary with the length of the n-alkane chain?
• RQ3 What is the sharpness of the superconducting transition (transition width) in these materials?
• RQ4 Do materials with longer alkane chains (≥16 carbons) exhibit Tc values beyond 504.24 K?
• RQ5 What is the role of the graphite-alkane interface in enabling high-Tc superconductivity?

Key findings

• Superconducting transitions were observed in n-alkane/graphite composites with critical temperatures ranging from 363.08 K to 504.24 K.
• The transition width for the highest-Tc sample was as narrow as 0.15 K, indicating a sharp, well-defined phase transition.
• Materials composed of n-alkanes with 16 or more carbon atoms exhibited superconducting transitions above 504 K.
• The critical temperature increased with alkane chain length, peaking at 504.24 K for C16 alkanes.
• The resistance drop during heating was abrupt and reproducible, supporting the presence of bulk superconductivity.
• The results suggest that the interface between n-alkanes and graphite plays a key role in enabling high-Tc superconductivity.