Magnetic Polarization and Fermi Surface Instability: Case of YbRh2Si2

TL;DR

This study investigates how magnetic field-induced Fermi surface changes in YbRh2Si2 lead to anomalies in thermoelectric power and resistivity, revealing a Lifshitz transition and non-Fermi liquid behavior at critical fields.

Contribution

It provides experimental evidence of a Lifshitz-type Fermi surface transition in YbRh2Si2 under high magnetic field, linking it to non-Fermi liquid phenomena.

Findings

Anomalies in thermoelectric power and resistivity at H_0 ~ 9.5 T

Sign change in thermoelectric power across the transition

Logarithmic divergence of S/T near critical field

Abstract

We report thermoelectric and resitivity measurements of antiferromagnetic heavy fermion compound YRh2Si2 at low temperatures down and under high magnetic field. At low temperature, the thermoelectric power and the resistivity present several distinct anomalies as a function of field around H_0 ~ 9.5 T when the magnetic polarization reaches a critical value. The anomalies are accompanied with a change of sign from negative at low magnetic field to positive at high field (H>H_0) and are resulting from a Lifshitz-type topological transition of the Fermi surface. A logarithmic divergence of S/T at T \to 0 K just above H_0 (H=11.5 T) is quite comparable to the well known divergence of S/T in the temperature range above the antiferromagnetic order at H=0 T referred to as non Fermi liquid behavior. The transition will be compared to the well characterized Fermi surface change in CeRu2Si2 at its pseudo-metamagnetic transition.