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TT: Tiefe Temperaturen

TT 7: Superconductivity & Solids At Low Temperature - Poster Session

TT 7.23: Poster

Montag, 27. März 2006, 14:00–17:45, P1

Theory of magnetic excitations in bilayer cuprates — •Hiroyuki Yamase and Walter Metzner — Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, D-70569, Stuttgart, Germany

We calculate the dynamical magnetic susceptibility Imχ(q,ω) in the bilayer t-J model in slave-boson mean-field approximation. At low temperature, where the d-wave superconducting state is realized, a pronounced peak in Imχ(q,ω) appears at q = Q = (π,π) and ω = ω_Q^res. For ω < ω_Q^res strong spectral weight spreads around Q, forming a diamond shaped pattern in q-space. This spectral weight is due to a collective mode, known as ”resonance mode” in the cuprates. The ω versus q dispersion of the mode is bent downwards around Q. For ω > ω_Q^res, strong signals of Imχ(q,ω) tracing an upward dispersion are found. In the normal state, Imχ(q,ω) exhibits only a broad maximum at q = Q, that is incommensurate signals appear only in the d-wave pairing state. The above results hold in both odd (q_z=π) and even (q_z=0) channels. The most relevant experimentally observed features of magnetic excitations in bilayer cuprates are well captured by slave-boson mean-field theory.