Regensburg 2002 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
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 7.43: Poster
Montag, 11. März 2002, 14:30–18:00, A
Exact ground states of highly frustrated quantum antiferromagnets in high magnetic fields — •A. Honecker1, J. Schulenburg2, J. Schnack3, J. Richter2, and H.-J. Schmidt3 — 1TU Braunschweig, Institut für Theoretische Physik, 38106 Braunschweig — 2Institut für Theoretische Physik, Universität Magdeburg, 39016 Magdeburg — 3Universität Osnabrück, Fachbereich Physik, 49069 Osnabrück
We construct exact eigenstates consisting of several independent, localized one-magnon states for the Heisenberg quantum antiferromagnet in certain frustrated geometries including Kagomé- and Pyrochlore-type lattices. These states turn out to be ground states for high magnetic fields. In many systems, the maximal number of local magnons scales with the size of the system, giving rise to a macroscopic jump in the zero-temperature magnetization curve just below the saturation field.
We verify this scenario for several models with spin 1/2 by numerical computation of their magnetization curve. These magnetization curves exhibit also plateaux, in particular just below the macroscopic magnetization jump. The latter plateau state is precisely the state with the maximal number of local magnons which in this case form a solid arrangement.