Lifshitz transition underlying the metamagnetic transition of UPt3

The magnetization process in heavy fermion systems, in which the f-electrons go from being part of the Fermi volume in the paramagnetic state, to being local moments in the fully polarized state, is still in question. Of particular interest is whether the f-electrons localize suddenly via a breakdown of Kondo screening, or gradually as the heavy fermion bands become spin polarized. Comparing quantum oscillation measurements, dc magnetoresistance measurements, and Fermi surfaces obtained from LDA calculations, we argue that the metamagnetic transition of UPt3, which occurs at an applied field $\mu_o H_M \sim 20$ T, coincides with a Lifshitz transition at which an open orbit on the band 2 hole-like Fermi surface becomes closed for one spin direction. At low field, proximity of the Fermi energy to this particular van Hove singularity may have implications for the superconducting pairing potential of UPt3. In our picture the magnetization comes from non-linear spin-splitting of the heavy fermion bands, not from suppression of Kondo screening. In support of this, we show that the non-linear field dependence of a particular quantum oscillation frequency can be fitted by assuming that the corresponding extremal Fermi surface area is proportional to the magnetization. This work was recently published as reference [1] below.

[1] A. McCollam, M. Fu and S.R. Julian, J. Phys.: Condens. Mat. 33 (2021) 075804.