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Title: Kondo breakdown versus spin-density-wave criticality in heavy-fermion metals
Plain: 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: 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 $\rho(T)$.
Settled by: Material-by-material measurements of Fermi volume on both sides of the critical point plus dynamical spin susceptibility scaling, compared with the two theories.
Kind: phenomenon
Answer type: classification
References: (empty)
Literature status: contested
Status note: (empty)
Posed since: 2001