Lifshitz transitions and quasiparticle de-renormalization in YbRh$_2$Si$_2$

TL;DR

This study investigates how magnetic fields influence the heavy fermion state of YbRh₂Si₂, revealing Lifshitz transitions and quasiparticle de-renormalization through Hall effect and magnetoresistance measurements at very low temperatures.

Contribution

It identifies Lifshitz transitions in YbRh₂Si₂ associated with heavy fermion bands and clarifies the nature of quasiparticle de-renormalization under magnetic fields.

Findings

Anomalies observed at three characteristic magnetic fields.

Lifshitz transitions linked to heavy fermion band changes.

Quasiparticle de-renormalization occurs smoothly.

Abstract

We study the effect of magnetic fields up to 15 T on the heavy fermion state of YbRh$_2$Si$_2$ via Hall effect and magnetoresistance measurements down to 50 mK. Our data show anomalies at three different characteristic fields. We compare our data to renormalized band structure calculations through which we identify Lifshitz transitions associated with the heavy fermion bands. The Hall measurements indicate that the de-renormalization of the quasiparticles, {\it i.e} the destruction of the local Kondo singlets, occurs smoothly while the Lifshitz transitions occur within rather confined regions of the magnetic field.