Quadrupole Order in the Frustrated Pyrochlore Tb2+xTi2-xO7+y
H. Takatsu, S. Onoda, S. Kittaka, A. Kasahara, Y. Kono, T. Sakakibara, Y. Kato, B. Fak, J. Ollivier, Jeffrey W. Lynn, T. Taniguchi, H. Kadowaki
A hidden order that emerges in the frustrated pyrochlore Tb2+xTi2-xO7+y with X = 0.005 > xc is studied from specific heat and magnetization experiments on a high-quality single crystal, as well as neutron scattering. Semi-quantitative3 analyses based on a pseudospin-1/2 pyrochlore Hamiltonian for ionic non-Kramers magnetic doublets indicate that it is a long-range of an electric quadrupole. These results suggest the existence for a Higgs phase located close to a U(1) quantum spin-liquid phase of the non-Kramers pyrochlore model.