Nonadiabatic electron-phonon coupling and its effects on superconductivity

Shi-Qi Hu; Xin-Bao Liu; Da-Qiang Chen; Chao Lian; En-Ge Wang; Sheng Meng

doi:10.1103/PhysRevB.105.224311

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Nonadiabatic electron-phonon coupling and its effects on superconductivity

Shi-Qi Hu, Xin-Bao Liu, Da-Qiang Chen, Chao Lian, En-Ge Wang, Sheng Meng

DOI 10.1103/PhysRevB.105.224311 · Physical Review B

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Abstract

As one of the most striking phenomena in many-body systems, the breakdown of the adiabatic Born-Oppenheimer (ABO) approximation is essential for understanding and predicting the dynamics of quantum materials. Here, we demonstrate that strong nonadiabatic (NA) effects can emerge in electron-phonon coupling (EPC) and resultant superconductivity, yielding a surprisingly large contribution (up to 20%) to the total EPC strength λ of doped graphene/graphane and modulating the superconductivity transition temperature Tc by ∼20%. The NA EPC, with a detectable isotopic effect, results from the renormalized EPC matrix elements (up to 40%) combined with the Fermi surface modulation, due to electron distributions deviating from the equilibrium. Our results imply that nonadiabaticity plays a wider and more important role than previously conceived, offering new understandings and strategies for dynamic engineering of quantum materials.