Anisotropic Breakdown of the Fermi Liquid at a Quantum Critical Point

Johnpierre Paglione, U of Maryland

Over the last 30 years, the concept of the nearly-free electron gas has been pushed to its limits with the discovery of the so-called "heavy-fermion" class of metals. In these materials, strong interactions between electrons can reduce their velocities by as much as 1000 times but still allow them to behave as free particles, retaining the essence of the standard model of condensed matter - Landau's Fermi liquid theory. However, a growing number of materials have been shown to strongly deviate from this picture when they are "pushed" through an absolute-zero-temperature, or quantum, phase transition. The speaker will provide an overview of tunable quantum instabilities and our experimental investigations of the CeMIn5 (M=Co, Rh, Ir) heavy-fermion system, focusing on the use of ultra-low-temperature heat and charge transport measurements to test the validity of the nearly-free electron picture directly at a quantum phase transition. Their studies have shown the first profound breakdown of Landau's theory, as manifested in the violation of a robust physical law which has stood for over 150 years.

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