Quantum Magnets under Pressure: Controlling Elementary Excitations in TlCuCl3

Rüegg, Ch.; Normand, B.; Matsumoto, M.; Furrer, A.; McMorrow, D.; Krämer, K.; Güdel, H. -U.; Gvasaliya, S.; Mutka, H.; Boehm, M.

Quantum Magnets under Pressure: Controlling Elementary Excitations in TlCuCl3

Authors

Description

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.
4 pages, 4 figures