MARK BARBER - Uniaxial Stress Technique and Investigations into Correlated Electron Systems

Mark Barber.

Max Planck Institute.

LUNES 11/12/2017, 14 hs.

Aula FEDERMAN, 1er piso, Pab. I.

Response to uniaxial distortion can be a powerful probe of the electronic properties of a solid. However, it is not a very commonly applied technique, chiefly because of the technical challenges of obtaining good strain homogeneity while applying significant pressures. In typical uniaxial pressure measurements, thin and wide samples are clamped between two anvils. Our approach uses a different, easier technique: cutting the sample into a long, narrow bar, and securing its two ends with epoxy across a piezoelectric driven vice.
In this talk I will introduce our new technique, presenting its unique capabilities, before moving on to describe results obtained on an unconventional superconductor Sr2RuO4.
The superconducting order parameter of Sr2RuO4 has long been speculated to be odd-parity. Of interest to us though is the close proximity of one of its three Fermi surfaces to a Van Hove singularity (VHs). Our results strongly suggest that we have been able to traverse the VHs, inducing a topological Lifshitz transition. Tc is enhanced by a factor ~2.3 and measurements of the normal state properties show that quasiparticle scattering is increased across all the bands and in all directions.
If time permits I will also mention further on going measurements tuning magnetic materials and further integration of the uniaxial stress technique with other experimental probes.