Dresden 2003 – scientific programme
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TT: Tiefe Temperaturen
TT 11: Postersitzung II (Metall-Isolator-Überg
änge, Phasenüberg
änge in Quantensystemen, Theorie: Systeme korrelierter Elektronen)
TT 11.45: Poster
Tuesday, March 25, 2003, 14:30–19:00, P2c, P2d
Magnetic excitations in two-leg and four-leg spin ladders — •Tamara Nunner1, Thilo Kopp1, and Markus Grüninger2 — 1EP VI, EKM, Universität Augsburg, 86135 Augsburg — 2II. Phys. Inst., Universtität zu Köln, 50937 Köln
Phonon assisted magnetic absorption provides a powerful tool to investigate the magnetic excitations of low dimensional antiferromagnets. In the two-dimensional undoped cuprates a bimagnon resonance has been identified[1] but the higher energy resonances are still unexplained[2]. In two-leg spin ladders a two-triplet bound state and a large continuum contribution has been observed[3], which is mainly due to three-triplet excitations[4]. Here, we use the Density Matrix Renormalization Group (DMRG) to investigate similar magnetic excitations in four-leg spin-ladders and discuss the crossover from two-leg ladders to the two-dimensional undoped cuprates.
[1] J. Lorenzana and G. A. Sawatzky, Phys. Rev. Lett. 74, 1867 (1995); Phys. Rev. B 52, 9576 (1995).
[2] M. Grüninger et al., Phys. Rev. B 62, 12422 (2000).
[3] M. Windt et al., Phys. Rev. Lett. 87, 127002 (2001).
[4] T. S. Nunner et al., Phys. Rev. B 66, 180404(R) (2002).