Multiple universalities in order-disorder magnetic phase transitions

Phase transitions in isotropic quantum antiferromagnets are associated with the condensation of bosonic triplet excitations. In three-dimensional quantum antiferromagnets, such as TlCuCl3, condensation can be either pressure or magnetic field induced. The corresponding magnetic order obeys universal scaling with thermal critical exponent phi. Employing a relativistic quantum field theory, the present work predicts the emergence of multiple (three) universalities under combined pressure and field tuning. Changes of universality are signaled by changes of the critical exponent phi. Explicitly, we predict the existence of two new exponents phi = 1 and 1/2 as well as recovering the known exponent phi = 3/2. We also predict logarithmic corrections to the power law scaling.