"Quantum phase transitions and disorder: Griffiths singularities, infinite randomness, and smearing"

Date: 
12/10/2013 - 3:30pm to 4:30pm
Location: 
CP 179
Speaker(s) / Presenter(s): 
Thomas Vojta (Missouri University)
Type of Event (for grouping events):
Phase transitions are fascinating phenomena in nature with consequences
ranging from the large scale structure of the universe to exotic quantum phases
at low temperatures. Many realistic systems contain impurities, defects and
other forms of quenched disorder. This talk explores the consequences of such
randomness on the properties of phase transitions.
At zero-temperature quantum phase transitions, randomness can have
particularly peculiar and strong effects. Often, rare strong disorder fluctuations
and the rare spatial regions that support them dominate the physics close to the
transition. They give rise to strong singularities in the free energy, the so-called
quantum-Griffiths singularities, In some systems such as metallic magnets, the
effects of rare fluctuations can be even stronger, leading to a destruction of the
phase transition by smearing. These general results are illustrated using experiments in transition
metal alloys and heavy fermion systems.
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