Quantum order by disorder and accidental soft mode Er2Ti2O7

M. E. Zhitomirsky, M. V. Gvozdikova, P. C. W. Holdsworth +1

Motivated by recent neutron scattering experiments, we derive and study an effective "pseudo-dipolar" spin-1/2 model for the XY pyrochlore antiferromagnet Er2Ti2O7. While a bond-de…