Regensburg 2002 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 7: Postersitzung I: Anwendungen der Supraleitung (1-6), Dünne Schichten, Josephsonkontakte, SQUIDs (7-17), Neue und unkonv. Supraleiter(18-23), Amorphe- und Tunnelsyst. (24-28), Quantenflüssigkeiten (29-30), Syst. korr. Elektr.: Theorie I (31-45)
TT 7.37: Poster
Montag, 11. März 2002, 14:30–18:00, A
The rotationally invariant approximation for the two-dimensional t-J model — •Michael Schreiber1 and Alexei Sherman2 — 1Institut für Physik, Technische Universität, D-09107 Chemnitz — 2Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia
Using the description in terms of the Hubbard operators hole and spin Green’s functions of the two-dimensional t-J model are calculated in an approximation which retains the rotation symmetry of the spin susceptibility in the paramagnetic state and has no predefined magnetic ordering. In this approximation, Green’s functions are represented by continued fractions which are interrupted with the help of the decoupling corrected by the constraint of zero site magnetization in the paramagnetic state. Results obtained in this approach for an undoped 32×32 lattice (the Heisenberg model) and for one hole in a 4×4 lattice are in good agreement with Monte Carlo and exact diagonalization data, respectively. In the limit of heavy doping the hole spectrum described by the obtained formulas acquires features of the spectrum of weakly correlated excitations.