Title: Tuning Iron-based Superconductors and Eu-based Semimetals by Pressure and Strain
When: Wednesday, March 22, (2023), 12:00
Place: Department of Condensed Matter Physics, Faculty of Sciences, Module 0, Conference Room (5th Floor).
Speaker: Elena Gati, Max-Planck-Institute for Chemical Physics of Solids, Dresden, Germany.
In recent years, driven by significant technical developments , pressure and strains of different symmetries have emerged as an excellent tool to tune the intriguing properties of quantum materials. In this talk, I will introduce the new capabilities, and demonstrate their potential using two material classes.
First, I will discuss the role of anisotropic strains in iron-based superconductors. Iron-based superconductors show – aside from high-temperature superconductivity – a variety of collective phenomena, including different types of magnetic order, orbital order and structural distortions. Among the different materials, CaKFe4As4 is known as an exceptional member of the iron-based superconductor family , since it (i) exhibits a very high critical temperature of Tc ~35 K in its stoichiometric form, and (ii) is located in the proximity of a hedgehog spin-vortex crystal (SVC) magnetic order, rather than a stripe-type spin-density wave (SSDW) order, as found in the majority of iron-based superconductors. By using anisotropic strains as a tuning parameter in CaKFe4As4, we find that we can tune the relative stability of SVC and SSDW orders, and tune superconducting Tc. Our results  allow us to disentangle the relative importance of different magnetic orders for stabilizing high Tc’s.
Second, I will discuss the case of Eu-based semimetals EuCd2X2 (X = As, P, etc.), which are particularly promising material platforms to study the interplay of band topology and magnetism. Our results  demonstrate that the magnetism can be sensitively tuned by hydrostatic and uniaxial pressures, allowing for the possibility of efficient tuning of band topology in laboratory settings.
Work is supported by the Max-Planck-Society and the German Science Foundation through grants TRR 288—422213477 and SFB 1143 (project-id 247310070).
- EG et al., Annalen der Physik, 2000248 (2020) (invited review article).
- Meier et al., npj Quantum Materials 3, 5 (2018).
- Zuniga, …, EG, in preparation (2023).
- EG et al., Phys. Rev. B 104, 155124 (2021).