Abstract
The representative cuprate with and is studied via first-principles calculations in the high-temperature tetragonal (HTT), low-temperature orthorhombic (LTO), and low-temperature less-orthorhombic (LTLO) structures. By suppressing the magnetism and superconductivity, the LTLO phase, which has rarely been observed in , is found to be the ground state where the structural phase transitions can be understood via phonon instability. Although the La-O composition is identified to be responsible for the phonon softening, the superconducting layer is dynamically stable. The LTLO phase, which can exhibit an splitting in the density of states, is proposed to have an intimate relationship with the observed pseudogap and the charge-density wave giving the stripe. We argue that at low temperatures, the superconducting LTO competes with the phonon-preferred LTLO phase by spontaneously forming the Cooper pairs, resulting in suppressing the stripe. Therefore, the revealed LTLO phase is indispensable for understanding .
- Received 16 April 2021
- Revised 11 August 2021
- Accepted 16 August 2021
DOI:https://doi.org/10.1103/PhysRevB.104.064114
©2021 American Physical Society