Kondo breakdown versus spin-density-wave criticality in heavy-fermion metals
In plain words
At a heavy-fermion quantum critical point either magnetism appears while the f electrons stay bound to conduction electrons, or the binding itself (Kondo screening) breaks down; which happens decides the theory.
Precise statement
For heavy-fermion quantum critical points (CeCu6-xAux, YbRh2Si2, CeRhIn5 under pressure, CeCoIn5), determine whether criticality is of Hertz-Millis-Moriya spin-density-wave type with Kondo screening intact, or of local (Kondo breakdown) type in which the f electrons leave the Fermi volume at the critical point. An answer classifies the known materials using $\omega/T$ scaling of the dynamical spin susceptibility, the Fermi-volume change, and the exponents of $C/T$ and $\rho(T)$.
What would settle it
Material-by-material measurements of Fermi volume on both sides of the critical point plus dynamical spin susceptibility scaling, compared with the two theories.
Related problems
- More general than Does the Fermi volume of YbRh2Si2 jump at its critical field
- More general than Kondo breakdown transition in a gate-tuned moire Kondo lattice