Local Moment and Heavy Fermion Physics

This theoretical research is in the area of heavy electron physics. This subject occupies a modest yet vital corner in current research into correlated materials. Many of the fundamental questions, such as how magnetism emerges and the nature of the non-Fermi liquid metal that develops around quantum criticality, are pressing problems to the field as a whole. Part of the work to be undertaken is motivated by a new range of experiments that fine-tune heavy fermion materials to a quantum phase transition. The development of new techniques, models and concepts to understand heavy electron materials and their critical behavior is a central element of this research.

The following subjects will be studied:

Field-tuned quantum criticality: The underscreened Kondo impurity model provides an example of field-tuned quantum criticality, with a Fermi temperature which can be driven continuously to zero. Using a lattice generalization of this model as a starting point, we will model the evolution of magnetically heavy electron systems in their approach to quantum criticality.

Frustrated heavy electron materials: We will study the interplay of frustration and the Kondo effect in Hund's coupled transition metal oxides.

Hidden order and nodal charge density wave formation: We will study two band systems to develop a theory for hidden order in URu2Si2.

A new Z2 Majorana approach to local moment physics: This will allow us to read-off spin correlators from the Majorana propagator, avoiding vertex correction difficulties encountered in conventional schemes. This new method will be applied to the single impurity and lattice Kondo model.

Density of state correlations in pseudogap systems: Inspired by the analogy with the Brown-Twiss interferometry of astrophysics, we will develop a method to extract information order parameter correlations from density of state fluctuations measured in scanning tunneling microscopy.

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This grant supports theoretical research on the physics of strongly correlated heavy electron systems. The research is at the forefront of modern condensed matter physics and will contribute to the foundations of fundamental physics. The participation of graduate students and postdoctoral research associates will ensure that future generations of theorists will be trained in these important areas. Like much of condensed matter physics, the research also has the potential to influence the development and applications of new materials.

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