Orbital-selective Mott transitions: Heavy fermions and beyond

TL;DR

This paper reviews the concept of orbital-selective Mott transitions, especially in heavy-fermion metals, discussing theoretical frameworks, quantum critical properties, and experimental interpretations related to the breakdown of the Kondo effect.

Contribution

It provides a comprehensive review of theoretical descriptions and experimental evidence for orbital-selective Mott transitions in correlated electron systems.

Findings

Orbital-selective Mott transitions explain Fermi surface changes in heavy-fermion metals.

Theoretical models distinguish different low-temperature phases.

Experimental data supports the relevance of orbital-selective Mott physics.

Abstract

Quantum phase transitions in metals are often accompanied by violations of Fermi liquid behavior in the quantum critical regime. Particularly fascinating are transitions beyond the Landau-Ginzburg-Wilson concept of a local order parameter. The breakdown of the Kondo effect in heavy-fermion metals constitutes a prime example of such a transition. Here, the strongly correlated f electrons become localized and disappear from the Fermi surface, implying that the transition is equivalent to an orbital-selective Mott transition, as has been discussed for multi-band transition-metal oxides. In this article, available theoretical descriptions for orbital-selective Mott transitions will be reviewed, with an emphasis on conceptual aspects like the distinction between different low-temperature phases and the structure of the global phase diagram. Selected results for quantum critical properties will be listed as well. Finally, a brief overview is given on experiments which have been interpreted in terms of orbital-selective Mott physics.