| DATE: |
2004-06-30 10:00 - 11:00 |
| PLACE: |
4-go-kan, 2F, Rinko-shitsu 1 |
| TITLE: |
Excitations in One-Dimensional and Quasi-One-Dimensional Spin Liquids |
| SPEAKER: |
Professor Goetz S. Uhrig (Institut fur Theoretische Physik, Universitat zu Koln, Germany) |
| LANGUAGE: |
English |
| URL: |
http://pfwww.kek.jp/pf-seminar/ |
| ABSTRACT: |
Low-dimensional quantum antiferromagnetism is characterized by the weakness or even absence of long-range order. Thus one has to deal with so-called spin liquids. The elementary excitations of such systems have mostly spin S=1; they are triplons [1]. We calculate the dispersion of such triplons and the resulting spectral functions of dimerized spin chains [2], of spin ladders [3] and of coupled spin ladders. The results are relevant for inelastic neutron scattering and inelastic light scattering and for optical absorption.
In particular, we show how the result for a one-dimensional system can be extended to a quasi one-dimensional systems by perpendicular couplings. The magnetic structure factor S(¦Ø) observed in striped cuprate superconductors [4] is explained in this way. A crossover is found from magnon-like to triplon-like excitations as function of energy.
[1] K.P.Schmidt, G.S.Uhrig, Phys.Rev. Lett.90, 227204 (2003)
[2] K.P.Schmidt, C.Knetter, G.S.Uhrig, Phys.Rev.B, in press, cond-mat/0307678
[3] C.Knetter, K.P.Schmidt, M.Gruninger, G.S.Uhrig, Phys. Rev. Lett.87, 167204 (2001);
K.P.Schmidt, C.Knetter, M.Gruninger, G.S.Uhrig, Phys.Rev.Lett 90, 167201 (2003)
[4] J.M.Tranquada et al., Nature .429, 534 (2004) |
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