Absence of electron-phonon coupling superconductivity in the bilayer phase of La3Ni2O7 under pressure

Abstract An experimental study found superconductivity in bilayer phase of La3Ni2O7, with the highest superconducting transition temperature (T c ) ∼ 80 K under pressure. Recently, some reports claimed that there exists a competitive monolayer-trilayer structural phase in La3Ni2O7 compounds. We perform the first-principles calculations and find that bilayer phase of La3Ni2O7 is energetically favorable under pressure. Although extensive studies have been done to investigate the electronic correlation and potential superconducting pairing mechanism in bilayer phase of La3Ni2O7, the phonon properties and electron-phonon coupling (EPC) in the high-pressure I4/mmm phase of La3Ni2O7 are not reported. Using the density functional theory (DFT) combined with Wannier interpolation technique, we study the phonon properties and EPC in bilayer phase of La3Ni2O7 under 29.5 GPa. Our findings reveal that EPC is insufficient to explain the observed superconducting T c ∼ 80 K. And the calculated Fermi surface nesting may explain the experimentally observed charge density wave (CDW) transition in bilayer phase of La3Ni2O7. Our calculations substantiate that bilayer phase of La3Ni2O7 is an unconventional superconductor.