Elastoresistance as probe of strain-controlled entropy from Kondo scattering

TL;DR

This study uses symmetry-resolved elastoresistance measurements on YbRh₂Si₂ to reveal how strain influences Kondo scattering and magnetic entropy, providing insights into strain-controlled quantum criticality in heavy-fermion systems.

Contribution

It introduces a symmetry-decomposed elastoresistance technique to probe strain-dependent Kondo scattering and quantum criticality in a prototypical heavy-fermion material.

Findings

Elastoresistance in the $A_{1g}$ channel shows sign changes and large low-temperature values.

Strain influences the magnetic entropy via Kondo scattering, indicating strain-controlled quantum criticality.

Symmetry analysis reveals negligible responses in symmetry-breaking channels.

Abstract

Heavy-fermion metals are prototype correlated electron systems for the study of Kondo entanglement and quantum criticality. We use the symmetry decomposed elastoresistance to uncover the fingerprints of strain-dependent Kondo scattering as function of temperature and magnetic field in the prototypical tetragonal Kondo lattice YbRh$_2$Si$_2$. By combining longitudinal and transverse resistance measurements under uniaxial strain applied along the tetragonal $[100]$ and $[110]$ directions, we obtain the elastoresistive responses in the $A_{1g}$, $B_{1g}$, and $B_{2g}$ symmetry channels. While the responses in the symmetry-breaking channels are negligible, the isotropic $A_{1g}$ elastoresistance displays characteristic sign changes and approaches huge values at low temperatures. Scaling analysis and comparison with linear thermal expansion measurements reveals that the elastoresistance probes the contribution of Kondo scattering to the strain dependence of magnetic entropy and signals strain-controlled quantum criticality upon cooling to 2 K.