Elucidation of Spin-Correlations, Fermi Surface and Pseudogap in a Copper Oxide Superconductor

• Published in: Condensed matter Vol. 8; no. 2; p. 33
• Main Authors: Kamimura, Hiroshi, Araidai, Masaaki, Ishida, Kunio, Matsuno, Shunichi, Sakata, Hideaki, Sasaoka, Kenji, Shiraishi, Kenji, Sugino, Osamu, Tsai, Jaw-Shen, Yamada, Kazuyoshi
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.06.2023
• Subjects: angle-resolved photoemission spectroscopy; Chemical elements; Copper; Copper oxides; Electron spin; Fermi surfaces; Fermi-pockets and -arcs; First principles; High temperature superconductors; high-Tc superconductor; Inelastic scattering; Kamimura–Suwa model; Mathematical analysis; neutron scattering; Neutrons; Particle spin; Phase diagrams; Phase transitions; Photoelectric emission; spin-correlation; Superconductivity; Superconductors; Transition temperature; Japan
• ISSN: 2410-3896; 2410-3896
• DOI: 10.3390/condmat8020033

First-principles calculations for underdoped La2−xSrxCuO4 (LSCO) have revealed a Fermi surface consisting of spin-triplet (KS) particles at the antinodal Fermi-pockets and spin-singlet (SS) particles at the nodal Fermi-arcs in the presence of AF local order. By performing a unique method of calculating the electronic-spin state of overdoped LSCO and by measurement of the spin-correlation length by neutron inelastic scattering, the origin of the phase-diagram, including the pseudogap phase in the high temperature superconductor, Sr-doped copper-oxide LSCO, has been elucidated. We have theoretically solved the long-term problem as to why the angle-resolved photoemission spectroscopy (ARPES) has not been able to observe Fermi pockets in the Fermi surface of LSCO. As a result, we show that the pseudogap region is bounded below the characteristic temperature T*(x) and above the superconducting transition temperature Tc(x) in the T vs. x phase diagram, where both the AF order and the KS particles in the Fermi pockets vanish at T*(x), whilst KS particles contribute to d-wave superconductivity below Tc. We also show that the relationship T*(xc) = Tc(xc) holds at xc = 0.30, which is consistent with ARPES experiments. At T*(x), a phase transition occurs from the pseudogap phase to an unusual metallic phase in which only the SS particles exist.