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TT: Fachverband Tiefe Temperaturen

TT 19: Correlated Electrons: Quantum-Critical Phenomena

TT 19.15: Vortrag

Dienstag, 26. Februar 2008, 18:00–18:15, H 3010

Probing field-induced quantum criticality in molecule-based low-dimensional spin systems — •Bernd Wolf¹, Yeekin Tsui¹, Ulrich Tutsch¹, Katarina Removic-Langer¹, Andrej Prokofiev¹, Wolf Aßmus¹, Roser Valenti², Stefan Wessel³, Andreas Honecker⁴, Matthias Wagner⁵, and Michael Lang¹ — ¹Physikalisches Institut, JWG-Universität Frankfurt; SFB/TRR49 — ²Institut für Theoretische Physik, JWG-Universität Frankfurt; SFB/TRR49 — ³Institut für Theoretische Physik, Universität Stuttgart — ⁴Institut für Theoretische Physik, Georg-August-Universität Göttingen — ⁵Institut für Anorganische und Analytische Chemie JWG-Universität Frankfurt; SFB/TRR49

A quantum critical point (QCP) is found in systems where a phase transition at T = 0 is driven by an external control parameter. Although a QCP takes place at T = 0, inaccessible by experiment, it has a significant influence on the physical properties over a wide range of temperature. Here we concentrate on field-induced QCPs in low-dimensional molecule-based spin systems. The molecular approach enables us to generate materials with magnetic exchange coupling constants weak enough for laboratory fields to drive the system into a new ground state. We present data of the magnetocaloric effect across the saturation field of an antiferromagnetic S = 1/2 Heisenberg chain system. These results compare favourably with theoretical predictions. In additon, we report thermodynamic measurements on the field-induced magnetic transition in coupled S = 1/2 dimer systems.