PT  - JOURNAL ARTICLE
AU  - Breunig, Oliver
AU  - Garst, Markus
AU  - Klümper, Andreas
AU  - Rohrkamp, Jens
AU  - Turnbull, Mark M.
AU  - Lorenz, Thomas
TI  - Quantum criticality in the spin-1/2 Heisenberg chain system copper pyrazine dinitrate
AID  - 10.1126/sciadv.aao3773
DP  - 2017 Dec 01
TA  - Science Advances
PG  - eaao3773
VI  - 3
IP  - 12
4099  - http://advances.sciencemag.org/content/3/12/eaao3773.short
4100  - http://advances.sciencemag.org/content/3/12/eaao3773.full
SO  - Sci Adv2017 Dec 01; 3
AB  - Low-dimensional quantum magnets promote strong correlations between magnetic moments that lead to fascinating quantum phenomena. A particularly interesting system is the antiferromagnetic spin-1/2 Heisenberg chain because it is exactly solvable by the Bethe-Ansatz method. It is approximately realized in the magnetic insulator copper pyrazine dinitrate, providing a unique opportunity for a quantitative comparison between theory and experiment. We investigate its thermodynamic properties with a particular focus on the field-induced quantum phase transition. Thermal expansion, magnetostriction, specific heat, magnetization, and magnetocaloric measurements are found to be in excellent agreement with exact Bethe-Ansatz predictions. Close to the critical field, thermodynamics obeys the expected quantum critical scaling behavior, and in particular, the magnetocaloric effect and the Grüneisen parameters diverge in a characteristic manner. Beyond its importance for quantum magnetism, our study establishes a paradigm of a quantum phase transition, which illustrates fundamental principles of quantum critical thermodynamics.