Fluctuation-induced first order transition due to Griffiths anomalies of the Cluster glass phase

摘要

In itinerant magnetic systems with disorder, the quantum Griffiths phase atT=0 is unstable to formation of a cluster glass (CG) of frozen droplet degreesof freedom. In the absence of the fluctuations associated with these degrees offreedom, the transition from the paramagnetic Fermi liquid (PMFL) to theordered phase proceeds via a conventional second-order quantum phasetransition. However, when the Griffiths anomalies due to the broad distributionof local energy scales are included, the transition is driven first-order via anovel mechanism for a fluctuation induced first-order transition. At highertemperatures, thermal effects restore the transition to second-order.Implications of the enhanced non-Ohmic dissipation in the CG phase are brieflydiscussed.