Abstract:

A quantum critical point occurs in a material as it undergoes a smooth transition from one ground state to another at absolute zero. It has been recognized as a mechanism for both unconventional superconductivity and non-Fermi liquid behavior. In this talk, I will review the basic aspects of quantum criticality and summarize some of the developments over the past decade or so. I will in particular consider the magnetic heavy fermion metals, in which extensive recent progresses have been made. Considerable experimental evidence has emerged for the theory of local quantum criticality, which invokes certain quantum entanglement effects beyond the order-parameter fluctuations. I will also briefly survey the relevant issues in a number of other strongly correlated electron systems -- including high temperature superconductors, quantum frustrated magnets, quantum nanostructures -- and in ultracold atoms in optical lattices.
 
 
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