Hidden competing phase revealed by first-principles calculations of phonon instability in the nearly optimally doped cuprate La1.875Sr0.125CuO4

doi:10.1103/PhysRevB.104.064114

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Title:	Hidden competing phase revealed by first-principles calculations of phonon instability in the nearly optimally doped cuprate La1.875Sr0.125CuO4
Authors:	Chi-Cheng Lee;Ji-Yao Chiu;Yukiko Yamada-Takamura;Taisuke Ozaki
Date:	2021-08-30
Issue Date:	2021-09-01 12:10:19 (UTC+8)
Abstract:	The representative cuprate La2−xMxCuO4 with M=Sr and x=1/8 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 La2−xSrxCuO4, is found to be the ground state where the structural phase transitions HTT→LTO→LTLO can be understood via phonon instability. Although the La-O composition is identified to be responsible for the phonon softening, the superconducting CuO2 layer is dynamically stable. The LTLO phase, which can exhibit an ∼20−meV 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 La1.875Sr0.125CuO4 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 La2−xSrxCuO4.
Relation:	PHYSICAL REVIEW B 104(6), 064114
DOI:	10.1103/PhysRevB.104.064114
Appears in Collections:	[Graduate Institute & Department of Physics] Journal Article

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