Restoration of quantum critical behavior by disorder in pressure-tuned (Mn,Fe)Si

Abstract

Quantum criticality: Iron aids restoration An exotic quantum state of matter is identified in a new material by researchers in the USA, Switzerland and Germany. Yasutomo Uemura from Columbia University and co-workers observe quantum criticality in a material in which it was previously unseen just by adding iron. As pressure is increasingly applied to pure manganese silicon at absolute zero temperature, it can suddenly change from an ordered magnetic state to an unordered one. Uemura et al. now show that a slower continuous, or second-order, transition is observed instead when fifteen percent of the manganese atoms are replaced with iron atoms. This is indicative that a quantum critical point exists at a pressure of between 21 and 23 kilobar. They believe that criticality is restored because the iron atoms introduce disorder into the system.