High-field evolution of Fermi-surface and quasiparticle properties

Characterize how the Fermi-surface volume, Fermi-surface topology, quasiparticle mass, and electronic g-factor evolve in heavy-fermion compounds subjected to large magnetic fields, including the effects of Kondo-singlet suppression and Zeeman spin splitting.

Background

The paper studies the heavy-fermion compound YbNi₄P₂ using high-field quantum-oscillation measurements. In heavy-fermion systems, magnetic fields suppress Kondo singlet formation and produce substantial Zeeman splitting, so the resulting composite quasiparticles can become progressively de-renormalized and their Fermi surfaces can undergo Lifshitz transitions or other reconstructions.

The authors identify the field dependence of the Fermi-surface volume, topology, quasiparticle mass, and electronic g-factor as an unresolved general problem. Their measurements provide information about these quantities in YbNi₄P₂, including a pronounced mass decrease and an abrupt frequency change near the putative Lifshitz transition at approximately 17 T, but the underlying high-field evolution is not fully established.

References

It remains an open question, how the Fermi surface volume, topology, quasiparticle mass, and $g$-factor evolve [5].

— Field-tuned quasiparticles and electronic structure in heavy-fermion YbNi4P2  (2608.28119 - Broad et al., 28 Aug 2026) in Introduction, paragraph beginning “In large magnetic fields”

Clearly, much lower temperatures and precise control of the ESR frequency would be required to check whether the ESR signal really converges to $g=2$.

— Evolution of electron spin resonance through a metallic quantum critical phase diagram  (2609.03994 - Scheffler et al., 3 Sep 2026) in Discussion and conclusion, paragraph comparing the ESR g factor with the proposed Kondo-breakdown scenario