Fractionalization and Fermi surface volume in heavy fermion compounds: the case of YbRh${}_2$ Si${}_2$

Abstract

We establish an effective theory for heavy fermion compounds close to a zero temperature Anti-Ferromagnetic (AF) transition. Coming from the heavy Fermi liquid phase across to the AF phase, the heavy electron fractionalizes into a light electron, a bosonic spinon and a {\it new} excitation: a spinless fermionic field. Assuming this field acquires dynamics and dispersion when one integrates out the high energy degrees of freedom, we give a scenario for the volume of its Fermi surface through the phase diagram. We apply our theory to the special case of YbRh${}_2$(Si${}_{1-x}$ Ge${}_x$)${}_2$ where we recover, within experimental resolution, several low temperature exponents for transport and thermodynamics.

4 pages, 5 figures