Resistivity in the Vicinity of a Van Hove Singularity: Sr$_2$RuO$_4$ Under Uniaxial Pressure

TL;DR

This study investigates how uniaxial pressure affects the resistivity and superconducting transition temperature of Sr$_2$RuO$_4$, revealing a Van Hove singularity's influence on electronic properties.

Contribution

It demonstrates that uniaxial pressure can tune the Fermi surface through a Van Hove singularity, altering resistivity behavior and superconductivity in a clean superconductor.

Findings

Resistivity changes from T^2 to T^{1.5} near the Van Hove singularity.

Superconducting T_c peaks at approximately 3.5 K under pressure.

Uniaxial pressure effectively probes electronic structure in pure samples.

Abstract

We report the results of a combined study of the normal state resistivity and superconducting transition temperature $T_c$ of the unconventional superconductor Sr$_2$RuO$_4$ under uniaxial pressure. There is strong evidence that as well as driving $T_c$ through a maximum at $\sim$3.5 K, compressive strains $\varepsilon$ of nearly 1 % along the crystallographic [100] axis drive the $\gamma$ Fermi surface sheet through a Van Hove singularity, changing the temperature dependence of the resistivity from $T^2$ above and below the transition region to $T^{1.5}$ within it. This occurs in extremely pure single crystals in which the impurity contribution to the resistivity is $<$100 n$\Omega$cm, so our study also highlights the potential of uniaxial pressure as a more general probe of this class of physics in clean systems.