Identify experimental fingerprints of Hund correlations

Identify experimental fingerprints that distinguish Hund correlations, including experimental observables capable of accessing the low-energy factor z_L^{avg} and the high-energy factor z_H through specific-heat and core-level XPS/XAS measurements.

Background

The paper introduces z_L{avg} as an average quasiparticle renormalization factor associated with low-energy mass enhancement and z_H as a measure of high-energy charge fluctuations. The authors note that specific heat can access the former, whereas the local charge-state distribution underlying z_H may be accessible through X-ray photoemission or absorption spectroscopy. Establishing experimentally identifiable fingerprints would therefore test and operationalize the proposed quantitative framework for Hundness in real materials.

References

Important remaining questions include the identification of experimental fingerprints of Hund correlations. While $z_L{avg}$, associated with the average quasiparticle mass enhancement, can be measured from specific heat, $z_H$ reflects the local charge-state distribution $P(N_{\mathrm{occ}\pm1)$, which is accessible to core-level spectroscopies such as X-ray photoemission/absorption spectroscopy (XPS/XAS).

— Universal Signature of Hundness and Its Quantification  (2608.14480 - Kim et al., 14 Aug 2026) in Main text, paragraph beginning “Important remaining questions include”