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

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.