First-Principles Electron-Phonon Interactions and Electron Spectral Functions in Lanthanum Cuprates

Cuprate high-temperature superconductors possess many unusual properties that are not completely understood. A striking one is their electron spectral function, which exhibits “pseudogaps” in angle-resolved photoemission spectroscopy (ARPES), violating conventional band theory. It is believed that both electronic correlations and electron-phonon (e-ph) interactions play a critical role in the cuprates. Even though much research has focused on hole-doped lanthanum cuprates, studies of the parent phase La₂CuO₄ (LCO) are rather limited. Because LCO is a Mott insulator, probing its electronic structure is difficult experimentally and also challenging theoretically due to the correlated d orbitals. 

In this work, we employ Hubbard-corrected density functional theory (DFT+U) and its linear-response extension to compute e-ph interactions in LCO with a correct treatment of electronic correlations [1]. Using a Hubbard-U value determined from first principles, we obtain band gap and magnetic moment in excellent agreement with experiments. Starting from this accurate ground state, we compute the temperature dependent electron spectral functions, employing a cumulant approach able to capture strong e-ph coupling, and find pronounced broadening and satellite peaks in the spectral functions. These results are a clear evidence for strong e-ph interactions and polaron effects in LCO. The talk will analyze these findings and contrast them with those for hole-doped LCO.