Quantum criticality in an organic magnet

Embargo until
Date
2006-06-30
Journal Title
Journal ISSN
Volume Title
Publisher
American Physical Society
Abstract
Exchange interactions between S=½ sites in piperazinium hexachlorodicuprate produce a frustrated bilayer magnet with a singlet ground state. We have determined the field-temperature phase diagram by high field magnetization and neutron scattering experiments. There are two quantum critical points: Hc1=7.5 T separates a quantum paramagnet phase from a three dimensional, antiferromagnetically ordered state while Hc2=37 T marks the onset of a fully polarized state. The ordered phase, which we describe as a magnon Bose-Einstein condensate (BEC), is embedded in a quantum critical regime with short range correlations. A low temperature anomaly in the BEC phase boundary indicates that additional low energy features of the material become important near Hc1.
Description
Keywords
high field magnetization, field-temperature phase diagram, singlet ground state, frustrated bilayer magnet, piperazinium hexachlorodicuprate, organic magnet, quantum criticality, paramagnetic-antiferromagnetic transitions, fully polarized state, paramagnetic materials, neutron diffraction, molecular magnetism, magnons, exchange interactions (electron), antiferromagnetic materials, magnon Bose-Einstein condensate, quantum critical regime
Citation
Physical Review Letters 30 June 2006, vol.96, no.25, pp. 257203/1-4