Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 27: CE: Poster Session
TT 27.65: Poster
Mittwoch, 24. März 2010, 14:00–18:00, Poster D1
Thermal expansion and magnetostriction of the spin-1/2-chain compound Cu(C4H4N2)(NO3)2 — •Jens Rohrkamp1, Yvonne Sanders1, Markus Garst2, Matt D. Phillips3, Mark M. Turnbull3, and Thomas Lorenz1 — 1II. Physikalisches Institut, Universität zu Köln, Germany — 2Institut für theoretische Physik, Universität zu Köln, Germany — 3Carlson School of Chemistry and Biochemistry, Clark University, USA
Compounds with magnetic subsystems representing simple model spin systems with weak magnetic coupling constants are ideal candidates to test theoretical predictions for the generic behavior close to quantum phase transitions. We present measurements of the thermal expansion and magnetostriction of the spin-1/2-chain compound copper pyrazine dinitrate Cu(C4H4N2)(NO3)2. Of particular interest is the low-temperature thermal expansion close to the saturation field Hc ≈ 14 T, which defines a quantum phase transition from the gapless Luttinger liquid state to the fully saturated state with a finite excitation gap. We find a sign change of the thermal expansion for the different ground states, and at the quantum critical point Hc the low-temperature expansion approaches a 1/√T divergence. Furthermore the magnetostriction data is compared to the spin-spin correlation function calculated via Bethe-Ansatz. This work was supported by the DFG through SFB 608.