Quantum phase transitions in bilayer SU(N) antiferromagnets

We present a detailed study of the destruction of SU(N) magnetic order in square lattice bilayer antiferromagnets using unbiased quantum Monte Carlo numerical simulations and field theoretic techniques. We study phase transitions from an SU(N) Néel state into two distinct quantum disordered "valence-bond" phases: a valence-bond liquid (VBL) with no broken symmetries and a lattice-symmetry-breaking valence-bond solid (VBS) state. For finite interlayer coupling, the cancellation of Berry phases between the layers has dramatic consequences on the two phase transitions: the Néel-VBS transition is first order for all N5 accesible in our model, whereas the Néel-VBL transition is continuous for N=2 and first order for N4; for N=3 the Néel-VBL transition show no signs of first-order behavior.