Einstein and Debye temperatures, electron-phonon coupling constant and a probable mechanism for ambient-pressure room-temperature superconductivity in intercalated graphite

Abstract

Recently, Ksenofontov et al (arXiv:2510.03256) observed ambient pressure room-temperature superconductivity in graphite intercalated with lithium-based alloys with transition temperature (according to magnetization measurements) $T_c=330$ $K$. Here, I analyzed the reported temperature dependent resistivity data $\rho (T)$ in these graphite-intercalated samples and found that $\rho (T)$ is well described by the model of two series resistors, where each resistor is described as either an Einstein conductor or a Bloch-Grüneisen conductor. Deduced Einstein and Debye temperatures are ${\Theta }_{E,1}\approx 250$ $K$ and ${\Theta }_{E,2}\approx 1,600$ $K$, and ${\Theta }_{D,1}\approx 300$ $K$ and ${\Theta }_{D,2}\approx 2,200$ $K$, respectively. Following the McMillan formalism, from the deduced ${\Theta }_{E,2}$ and ${\Theta }_{D,2}$, the electron-phonon coupling constant ${\lambda }_{e-ph}=2.2-2.6$ was obtained. This value of ${\lambda }_{e-ph}$ is approximately equal to the value of ${\lambda }_{e-ph}$ in highly compressed superconducting hydrides. Based on this, I can propose that the observed room-temperature superconductivity in intercalated graphite is localized in nanoscale Sr-Ca-Li metallic flakes/particles, which adopt the phonon spectrum from the surrounding bulk graphite matrix, and as a result, conventional electron-phonon superconductivity arises in these nano-flakes/particles at room temperature. Experimental data reported by Ksenofontov et al (arXiv:2510.03256) on trapped magnetic flux decay in intercalated graphite samples supports the proposition.

19 pages, 2 figures

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