paper

Field-induced criticality in a gapped quantum magnet with bond disorder

arXiv:1201.6143 · doi:10.1103/PhysRevB.85.100410

Abstract

Neutron diffraction and calorimetric measurements are used to study the field-induced quantum phase transition in piperazinium-Cu $_{2}$ (Cl $_{1 - x}$ Br $_{x}$ ) $_{6}$ ( $x = 0$ , x=3.5% and x=7.5%), a prototypical quantum antiferromagnet with random bonds. The critical indexes $I ¨ $ and $I^^{2}$ are determined. The findings contradict some original predictions for Bose Glass based on the assumption $z = d$ , but are consistent with recent theoretical results implying $z < d$ . Inelastic neutron experiments reveal that disorder has a profound effect on the lowest-energy magnetic gap excitation in the system.

4.2 pages, 4 figures. Submitted to PRB Rapid Communications