Regensburg 1998 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 21: Postersitzung III: Spin-Peierls-Systeme, Metall-Isolator-Übergang, Lokalisierung; SL: Theorie; Quantenflüssigkeiten und -kristalle; Amorphe Materialien, Tunnelsysteme; Borcarbide, Fullerene, konventionelle SL; SL dünner Filme; Experimentiertechniken
TT 21.41: Poster
Donnerstag, 26. März 1998, 15:00–18:30, D
The 2D t-J model in the quantum disordered regime — •A. Sherman1 and M. Schreiber2 — 1Institute of Physics, Riia 142, EE-2400 Tartu, Estonia — 2Institut für Physik, Technische Universität, D-09107 Chemnitz
We apply the modified spin-wave theory with the constraint of zero staggered magnetization to investigate normal-state spectral and magnetic properties of the 2D t-J model in the paramagnetic state. Self-energy equations for hole and magnon Green’s functions are solved numerically in the self-consistent Born approximation. The constraint can be fulfilled in the ranges of hole concentrations 0.02-0.6ex ∼< x-0.6ex ∼< 0.17 and temperatures T-0.6ex ∼< 100 K. In this region the hole spectrum is nonmetallic which is manifested in the variation with x of the quasiparticle weights of states and in the violation of Luttinger’s theorem. With decreasing x from x≈ 0.17 hidden parts appear in the hole Fermi surface which can be interpreted as the opening of the pseudogap near (±π,0), (0,±π). Obtained size, symmetry and concentration dependence of the pseudogap are in agreement with photoemission data in Bi2212. Calculated temperature dependencies of the spin correlation length, spin-lattice relaxation times at the Cu and O sites, and static susceptibility are typical for the quantum disordered regime. They are in qualitative and in some cases in quantitative agreement with experiment in underdoped YBa2Cu3O6+δ. At x-0.6ex ∼> 0.12 the considered nonmetallic phase borders the phase of conventional metal.