Program Results

Introduction to the event

Quantum materials possesses extraordinary properties due to quantum effect. To probe their properties, scientists apply external control knob to study the corresponding change, e.g. chemical doping, magnetic fields, pressure, etc. Recently uniaxial stress becomes a newly established approach to study quantum materials. Many intriguing quantum materials has their electrons tightly bonded on the lattice site. The way to make it conductive is through electron hopping from one site to another. The hopping strength is proportional to the overlap of wave function between the adjacent sites. In this regard, the application of uniaxial stress becomes a very useful probe to tune the materials because this directional stress probe can squeeze or expand the length of the lattice and therefore can alter the hopping strength. In addition, symmetry is an important aspect of physics. Uniaxial stress is a directional probe, which can break lattice symmetry. As a result, physical quantities protected by lattice symmetry will change accordingly. With these two main reasons in mind, one can measure different physical properties (transport, spectroscopy, thermodynamics, etc.) under uniaxial stress to study quantum materials. Our group is setting up this unique probe and, hopefully, will enrich the research capability of studying quantum materials in Taiwan.

Recently, we studied unconventional superconductor Sr₂RuO₄ whose superconductivity remains elusive even after almost 3 decades study. There are evidences showing that this compound has degenerate order parameter protected by its tetragonal lattice symmetry. Upon application of uniaxial stress, this degeneracy is expected to be lifted, leading to a splitting of transition temperature. Within our experimental resolution, we observed only a single transition temperature. This null results challenge our understanding of the unconventional superconductivity. For more details, please check Physical Review B 110, 064514 (2024).