2008/03/26 by Ch. Rüegg, B. Normand, M. Matsumoto +7 · 1 citation
Physics and Astronomy · #cond-mat.str-el
paper · pdf · doi:10.1103/physrevlett.100.205701
published as Phys. Rev. Lett. 100, 205701 (2008) · 4 pages, 4 figures
arxiv created 2008/03/26 · arxiv updated 2009/12/01
We follow the evolution of the elementary excitations of the quantum antiferromagnet TlCuCl3 through the pressure-induced quantum critical point, which separates a dimer-based quantum disordered phase from a phase of long-ranged magnetic order. We demonstrate by neutron spectroscopy the continuous emergence in the weakly ordered state of a low-lying but massive excitation corresponding to longitudinal fluctuations of the magnetic moment. This mode is not present in a classical description of ordered magnets, but is a direct consequence of the quantum critical point.