Front Cover (Phys. Status Solidi B 3/2010)
H. Kühne, M. Günther, S. Grossjohann, W. Brenig, F. J. Litterst, A. P. Reyes, P. L. Kuhns, M. M. Turnbull, C. P. Landee and H.-H. Klauss
Article first published online: 5 MAR 2010 | DOI: 10.1002/pssb.201090003
This Special Issue is guest-edited by Frank Steglich, Oliver Stockert, Steffen Wirth and contains selected papers that were presented at the International Conference on Quantum Criticality and Novel Phases (QCNP 2009). The cover picture refers to the Editor's Choice article by Hannes Kühne and co-workers on pages 671-675. It depicts the quantum critical behavior of the low frequency spin excitations in the magnetic field versus temperature diagram of the S = 1/2 antiferromagnetic Heisenberg chain system copper pyrazine dinitrate (CuPzN). The vertical parameter is the NMR spin-lattice relaxation rate T1−1, which is a measure for the density of spin excitations in this system. In the vicinity of the quantum critical point a drastic increase of T1−1 marks the transition between a Luttinger liquid and a fully polarized phase.