Quantum Criticality and Global Phase Diagram of Magnetic Heavy Fermions

Qimiao Si

doi:10.1002/pssb.200983082

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arXiv · 0912.0040

Quantum Criticality and Global Phase Diagram of Magnetic Heavy Fermions

Qimiao Si

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Abstract

Quantum criticality describes the collective fluctuations of matter undergoing a second-order phase transition at zero temperature. It is being discussed in a number of strongly correlated electron systems. A prototype case occurs in the heavy fermion metals, in which antiferromagnetic quantum critical points have been explicitly observed. Here, I address two types of antiferromagnetic quantum critical points. In addition to the standard description based on the fluctuations of the antiferromagnetic order, a local quantum critical point is also considered. It contains inherently quantum modes that are associated with a critical breakdown of the Kondo effect. Across such a quantum critical point, there is a sudden collapse of a large Fermi surface to a small one. I also consider the proximate antiferromagnetic and paramagnetic phases, and these considerations lead to a global phase diagram. Finally, I discuss the pertinent experiments on the antiferromagnetic heavy fermions, briefly address the case of ferromagnetic heavy fermions, and outline some directions for future studies.

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Qimiao Si. 2009-12-03. Quantum Criticality and Global Phase Diagram of Magnetic Heavy Fermions. https://doi.org/10.1002/pssb.200983082

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