Combining hydrostatic with uniaxial pressure to tune quantum materials

Tuning the properties of solids has been the key for the discovery of novel quantum states that result from electronic correlations as well as topological properties of the electronic wavefunction. In fact, many properties of these phases are governed by symmetry. In controlling quantum materials in general and symmetry specifically, physical pressure stands out for various reasons: Experimentally, an unprecedented high level of controllability can be achieved. In addition, pressure is very versatile: It can either act symmetry-breaking, when applied uniaxially, or can preserve symmetry, e.g., when applied hydrostatically. In recent years, it was for example possible to discover electronic liquid states in unconventional superconductors by deliberately breaking the symmetry of their crystal lattice via uniaxial pressure, or to find the first room-temperature superconductor by applying high hydrostatic pressures.

Miniaturization of uniaxial pressure device for use in hydrostatic pressure cells. The arrows on the cubes indicate the action of hydrostatic vs. uniaxial pressure.
 

It is the aim of the present project to go beyond the present state of the art and develop a novel type of tuning condensed matter systems based on the combination of hydrostatic and uniaxial pressure. This novel ansatz will allow to simultaneously and quasi-continuously control volume and symmetry of a given material. As such, we imagine this to be an approach to create novel states of matter similar to a chemistry-based approach, but with the great advantage of an inimitable level of fine-tunability.

Recent proof-of-principle experiments [1] have successfully demonstrated the feasibility of this new ansatz. In this project, you will continue to advance this experimental capability and apply it to the study of unconventional superconductors [2] in zero and high magnetic fields. The goal within this project is to deepen the understanding of the interplay of unconventional superconductivity with competing symmetry-broken states, such as magnetic or electron liquid states, close to quantum-critical points [3]. On the long term, we envision the technique, which is developed in this project, to be an exciting tuning route for the wider class of quantum materials.

We are looking for a PhD student with background in solid-state physics or materials science, who is interested in developing high-precision low-temperature instrumentation and applying this knowledge to the study of carefully selected quantum materials.

References

[1] E. Gati, L. Xiang, L. Bud'ko, and P.C. Canfield
Hydrostatic and Uniaxial Pressure Tuning of Iron-Based Superconductors: Insights into Superconductivity, Magnetism, Nematicity, and Collapsed Tetragonal Transitions
Annalen der Physik 532, 2000248 (2020)
[2] E. Gati, L. Xiang, L. Bud'ko, and P.C. Canfield
Measurements of elastoresistance under pressure by combining in-situ tunable quasi-uniaxial stress with hydrostatic pressure
Rev. Sci. Inst. 91, 023904 (2020)
[3] H.-H. Kuo, J.-H. Chu, J.C. Palmstrom, S.A. Kivelson, I.R. Fisher
Ubiquitous signatures of nematic quantum criticality in optimally doped Fe-based superconductors
Science 352, 958 (2016)

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