Quantum critical behaviour of the cluster glass phase

In disordered itinerant magnets with arbitrary symmetry of the order parameter, the conventional quantum critical point between the ordered phase and the paramagnetic Fermi-liquid (PMFL) is destroyed due to the formation of the cluster glass (CG) phase. In this talk, we will discuss the quantum critical behaviour at the CG-PMFL transition. We will show that fluctuations due to quantum Griffiths anomalies induce a first-order transition from the PMFL at T=0, while at higher temperatures a conventional continuous transition is restored. This is in contrast to the behaviour of a collection of identical droplets where the second-order transition persists down to T=0.