| Heavy fermion metals close to magnetic quantum phase transitions exhibit unusual properties, and therefore are promising systems to look for new quantum states of matter. In the first part of the talk an introduction to this topic will be presented. In the second part of the talk I will introduce the concept of breakdown of Kondo effect and present a study of the Kondo-Heisenberg model in three dimensions. The mean field phase diagram exhibits a spin liquid phase and a heavy-fermion phase, separated by a quantum critical point where an energy scale associated with Kondo hybridization vanishes. The transport and thermodynamic properties near this quantum critical point will be discussed in light of recent experiments on heavy fermion systems. |
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