Pressure-induced enhancement of electron-phonon coupling in superconducting CaC6 from first principles

Lijun Zhang; Yu Xie; Tian Cui; Yan Li; Zhi He; Yanming Ma; Guangtian Zou

doi:10.1103/PhysRevB.74.184519

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Pressure-induced enhancement of electron-phonon coupling in superconducting CaC6 from first principles

Lijun Zhang, Yu Xie, Tian Cui, Yan Li, Zhi He, Yanming Ma, Guangtian Zou

DOI 10.1103/PhysRevB.74.184519 · Physical Review B

T1

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Abstract

The pressure effects on the electron-phonon coupling (EPC) in superconducting CaC6 have been extensively studied using first-principles calculations within the rigid muffin-tin approximation. It is found that pairing electrons are mainly attributed to the Ca 3d electrons mediated by Ca low-lying, in-plane phonon vibrations. An increase in mean square of the EPC matrix element ⟨I2⟩ and a decrease in Ca low-lying phonon frequency with increasing pressure are mainly responsible for the experimental observation of enhanced superconducting transition temperature. Furthermore, Mulliken population analysis suggests that the pressure-induced charge transfers from Ca to the graphite layers might mainly contribute to the softening behavior of Ca in-plane phonons.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
CaC6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	11.5	Pressure unresolved	unknown
CaC6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	15.1	8 GPa	unknown
CaC6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	5	10 GPa	unknown
CaC6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	Pressure unresolved	unknown
CaC6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	5 GPa	unknown
CaC6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	—	10 GPa	unknown