2006/02/07 by Hiroyuki Yamase, Walter Metzner · 3 citations
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Condensed matter physics #Magnetic and transport properties of perovskites and related materials #Omega #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.73.214517
published as Phys. Rev. B 73, 214517 (2006) · 50 pages, 20 figures
arxiv created 2006/02/07 · openalex publication_date 2006/06/15 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We perform a comprehensive analysis of the dynamical magnetic susceptibility \ensuremathχ(q,\ensuremathω) in the slave-boson mean-field scheme of the bilayer t-J model. We use model parameters appropriate for YBa2Cu3O6+x (YBCO), a typical bilayer high-Tc cuprate compound well studied by neutron scattering experiments. In the d-wave pairing state, the strongest magnetic spectral weight appears at q=Q\ensuremath≡(\ensuremathπ,\ensuremathπ) and \ensuremathω=\ensuremathωQres, and spreads into a diamond-shaped shell around Q in q space for \ensuremathω<\ensuremathωQres. This weight is due to a collective mode, namely a particle-hole bound state, which has a downward \ensuremathω versus q dispersion around Q. Within the high intensity shell, the incommensurate (IC) signals at q=(\ensuremathπ,\ensuremathπ\ifmmode±\else\textpm\fi2\ensuremathπ\ensuremathη) and (\ensuremathπ\ifmmode±\else\textpm\fi2\ensuremathπ\ensuremathη,\ensuremathπ) tend to be stronger than the diagonal incommensurate (DIC) signals at q=(\ensuremathπ\ifmmode±\else\textpm\fi2\ensuremathπ\ensuremathη^\ensuremath',\ensuremathπ\ifmmode±\else\textpm\fi2\ensuremathπ\ensuremathη^\ensuremath'), especially for a large hole density \ensuremathδ. For \ensuremathω\ensuremath≪\ensuremathωQres the IC signals completely disappear and the weight remains only around the DIC positions. For \ensuremathω>\ensuremathωQres strong signals of Im\phantom\rule0.2em0ex\ensuremathχ(q,\ensuremathω) tracing an upward dispersion are found and interpreted as an overdamped collective excitation near \ensuremathωQres. In the normal state, Im\ensuremathχ(q,\ensuremathω) has a broad peak at q=Q. That is, the IC and DIC signals appear only in the d-wave pairing state. We also study effects of a small orthorhombic anisotropy, which is intrinsic in untwinned YBCO crystals. Because of electron-electron correlations favoring d-wave shaped Fermi surface deformations, we expect an enhanced anisotropy of magnetic excitation spectra. This effect is particularly pronounced for low \ensuremathδ and at relatively high temperature. The present theory provides a rather detailed microscopic explanation of the most salient properties of magnetic excitations observed in YBCO.