Hall Number in YbRh2Si2

TL;DR

This paper investigates the abrupt change in the Hall number at a quantum critical point in YbRh2Si2, attributing it to small valence fluctuations affecting the Fermi surface, and proposes it as a quantum critical valence fluctuator.

Contribution

It provides a theoretical calculation linking Fermi surface changes and valence fluctuations to the Hall number jump in YbRh2Si2.

Findings

Fermi surface is multi-sheeted with opposite sign contributions.

Small f electron occupation changes reproduce Hall number jump.

YbRh2Si2 may be a quantum critical valence fluctuator.

Abstract

Recent experimental studies have revealed an abrupt change in the Hall number at a field tuned quantum critical point in the heavy fermion magnet YbRh2Si2. We investigate this by calculating the local density band structure for this metal and the appropriate transport integrals. We find the Fermi surface to be multi-sheeted with the two largest sheets having opposite sign contributions to the Hall number. Small changes in the f electron occupation are sufficient to reproduce the observed large change in the Hall number. This suggests that YbRh2Si2 may be the first example of a quantum critical valence fluctuator.